InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1051. |
There are three urns containing 2 white and 3 black balls, 3 white and 2 black balls and 4 white and 1 black balls, respectively. There is an equal probability of each urn being chosen. A ball is drawn at random from the chosen urn and it is found to be white. Find the probability that the ball drawn was from the second urn. |
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Answer» Let `U_(1)`={2 white, 3 black balls} `U_(2)`={3 white , 2 black balls} and `U_(3)`={4 white ,1 black balls} `thereforeP(U_(1))=P(U_(2))=P(U_(3))=1/3` Let `E_(1)` be the event that a ball is chosen from urn U, E be the event that a ball is chosen from urn `U_(1)` and `E_(2)` be the event that a ball is chosen from urn `U_(2)` and `E_(3)` be the event that a ball is chosen from urn `U_(3)`. Also, `P(E_(1))=P(E_(2))=P(E_(3))=1//3` Let E be the event that white ball is drawn `therefore P(E//E_(1))=2/5,P(E//E_(2))=3/5,P(E//E_(3))=4/5` Now, `P(E_(2)//E)=(P(E_(2))cdotP(E//E_(2)))/(P(E_(1))cdotP(E//E_(1))+P(E_(2))cdotP(E//E_(2))+P(E_(3))cdotP(E//E_(3)))` `=(1/3cdot3/5)/(1/3cdot2/5+1/3cdot3/5+1/3cdot4/5)` `=(3/15)/(2/15+3/15+4/15)=3/9=1/3` |
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| 1052. |
A cube having all of its sides painted is cut by two horizontal, two vertical, and other two planes so as to form 27 cubes all having the same dimensions. Of these cubes, a cube is selected at random. The total number of cubes having at least one of its sides painted isA. 14B. 18C. 22D. 26 |
| Answer» Correct Answer - (d) | |
| 1053. |
In an objective paper, there are two sections of 10 questions each.For "section 1", each question has 5 options and only one optionis correct and "section 2" has 4 options with multiple answers and marks for a question in this section is awarded only if he ticks all correct answers. Marks for each question in "sectionl 1" is 1 and in "section 2" is 3. (There is no negative marking.) If a candidate attempts only two questions by guessing, one from "section 1" and one from "section 2", the probability that he scores in both question is `74/75`A. `74//75`B. `1//25`C. `1//15`D. `1//75` |
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Answer» Correct Answer - D Let `p_(1)` be the probability of being an answer correct from section 1. Then `p_(1)=1//5.` Let `p_(2)` be the probability of being an answer correct from section 2. Then `p_(2)=1//15.` Hence, the required probability is `1//5 xx1//15=1//75.` |
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| 1054. |
There are n students in a class. Ler `P(E_lambda)` be the probability that exactly `lambda` out of n pass the examination. If `P(E_lambda)` is directly proportional to `lambda^2(0lelambdalen)`. If a selected student has been found to pass the examination, then the probability that he is the only student to have passed the examination, isA. `(1)/(sumn)`B. `(1)/(sumn^2)`C. `(1)/(sumn^3)`D. `(1)/(sumn^4)` |
| Answer» Correct Answer - (c) | |
| 1055. |
There are n students in a class. Ler `P(E_lambda)` be the probability that exactly `lambda` out of n pass the examination. If `P(E_lambda)` is directly proportional to `lambda^2(0lelambdalen)`. Proportional constant k is equal toA. 0.25B. 0.5C. 0.75D. 0.35 |
| Answer» Correct Answer - (c) | |
| 1056. |
There are n students in a class. Ler `P(E_lambda)` be the probability that exactly `lambda` out of n pass the examination. If `P(E_lambda)` is directly proportional to `lambda^2(0lelambdalen)`. Proportional constant k is equal toA. `(1)/(sumn)`B. `(1)/(sumn^2)`C. `(1)/(sumn^3)`D. `(1)/(sumn^4)` |
| Answer» Correct Answer - (b) | |
| 1057. |
In a class of 10 student, probability of exactly I students passing an examination is directly proportional to `i^(2).` Then answer the following questions: If a students selected at random is found to have passed the examination, then the probability that he was the only student who has passed the examination isA. `1//3025`B. `1//605`C. `1//275`D. `1//121` |
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Answer» Correct Answer - A Let P(i) be the probability that exactly I students are passing an examination. Now given that `P(A_(i))=lamda_(i)^(2)(where lamda"is constant")` `impliesunderset(i-1)overset(10)sumP(A_(i))=underset(i-1)overset(10)sum lamdai^(2)=lamda(10xx11xx21)/(6)=lamdaxx386=1` `implieslamda =1//358=5//77.` Let A reprsent the event that selected students have passed the examination. Therefore, `P(A)underset(i-1)overset(10)sumP(A//A_(i))P(A_(i))` `=underset(i-1)overset(10)sum(i)/(10)(i^(2))/(358)` `=(1)/(3850)underset(i-1)overset(10)sumi^(3` `=(10^(2)xx11^(2))/(4xx3850)=11/14` Now ` P(A_(i)//A)=((PA//A_(i))P(A_(i)))/(P(A))` `=(1/358xx1/10)/(11/14)` `=(1)/(11xx55)xx1/5=1/3025` |
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| 1058. |
In a class of 10 student, probability of exactly I students passing an examination is directly proportional to `i^(2).` Then answer the following questions: If a student is selected at random, then the probability that he has passed the examination isA. `1//7`B. `11//35`C. `11//14`D. None of these |
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Answer» Correct Answer - C Let P(i) be the probability that exactly I students are passing an examination. Now given that `P(A_(i))=lamda_(i)^(2)(where lamda"is constant")` `impliesunderset(i-1)overset(10)sumP(A_(i))=underset(i-1)overset(10)sum lamdai^(2)=lamda(10xx11xx21)/(6)=lamdaxx386=1` `implieslamda =1//358=5//77.` Let A reprsent the event that selected students have passed the examination. Therefore, `P(A)underset(i-1)overset(10)sumP(A//A_(i))P(A_(i))` `=underset(i-1)overset(10)sum(i)/(10)(i^(2))/(358)` `=(1)/(3850)underset(i-1)overset(10)sumi^(3` `=(10^(2)xx11^(2))/(4xx3850)=11/14` Now ` P(A_(i)//A)=((PA//A_(i))P(A_(i)))/(P(A))` `=(1/358xx1/10)/(11/14)` `=(1)/(11xx55)xx1/5=1/3025` |
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| 1059. |
In a class of 10 student, probability of exactly I students passing an examination is directly proportional to `i^(2).` Then answer the following questions: The probability that exactly 5 students passing an examination isA. `1//11`B. `5//77`C. `25//77`D. `10//77` |
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Answer» Correct Answer - B Let P(i) be the probability that exactly I students are passing an examination. Now given that `P(A_(i))=lamda_(i)^(2)(where lamda"is constant")` `impliesunderset(i-1)overset(10)sumP(A_(i))=underset(i-1)overset(10)sum lamdai^(2)=lamda(10xx11xx21)/(6)=lamdaxx386=1` `implieslamda =1//358=5//77.` Let A reprsent the event that selected students have passed the examination. Therefore, `P(A)underset(i-1)overset(10)sumP(A//A_(i))P(A_(i))` `=underset(i-1)overset(10)sum(i)/(10)(i^(2))/(358)` `=(1)/(3850)underset(i-1)overset(10)sumi^(3` `=(10^(2)xx11^(2))/(4xx3850)=11/14` Now ` P(A_(i)//A)=((PA//A_(i))P(A_(i)))/(P(A))` `=(1/358xx1/10)/(11/14)` `=(1)/(11xx55)xx1/5=1/3025` |
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| 1060. |
A bag contains 3 red and 4 black balls and another bag has 4 red and 2 black halls. One bag is selected at random and from the selected bag a ball Is drawn. Let E be the event that the first bag is selected, F b the event that the second bag is selected. G be the event that ball drawn Is red. Find (a) P(E) (b) P(F) (c) P(G/E) (d) P(G/F) |
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Answer» Let E: First bag is selected (a) P(E) = \(\frac{1}{2}\) F: Second bag is selected G: Ball is red (b) P(F) = \(\frac{1}{2}\) G: Ball is Red (c) P (G/E) = P (red ball from I bag) = \(\frac{3}{4}\) (d) P(G/F)= P(red ball from Il bag) = \(\frac{4}{6}\) = \(\frac{2}{3}\) |
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| 1061. |
A bag contains 4 red and 4 black balls, another bag contains 2 red and 6 black balls. One of the two bags is selected at random and a ball is drawn from the bag which is found to be red. Find the probability that the ball is drawn from the first bag. |
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Answer» Let E1 : first bag is selected, E2 : second bag is selected Then, E1 and E2 are mutually exclusive and exhaustive. Moreover, P(E1) = P(E2) = 1/2 Let E : ball drawn is red. P(E/E1) = P(drawing a red ball from first bag) = 4/8 = 1/2 P(E/E2) = P(drawing a red ball from second bag) = 2/8 = 1/4 By using Baye’s theorem, Required probability = P(E1/E) = (P(E1)P(E/E1))/(P(E1)P(E/E1) + P(E2)P(E/E2)) = (1/2 x 1/2)/(1/2 x 1/2 + 1/2 x 1/4) = (1/4)/(1/4 + 1/8) = (1/4)/(2 + 1)/8 = (1/4)/(3/8) = 2/3 |
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| 1062. |
In answering a question on a multiple choice test, a student either knows the answer or guesses. Let 3/4 be the probability that he knows the answer and 1/4 be the probability that he guesses. Assuming that a student who guesses at the answer will be correct with probability 1/4 . What is the probability that the student knows the answer given that he answered it correctly? |
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Answer» Let E1 : the event that the student knows the answer and E2 : the event that the student guesses the answer. Then, E1 and E2 are mutually exclusive and exhaustive. Moreover, P(E1) = 3/4 and P(E2) = 1/4 Let E : the answer is correct. The probability that the student answered correctly, given that he knows the answer, is 1 i.e., P P(E/E1) = 1 Probability that the students answered correctly, given that the he guessed, is 1/4 i.e., P(E/E2) = 1/4 By using Baye’s theorem, we obtain P(E1/E) = (P(E1)P(E/E1))/(P(E1)P(E/E1) + P(E2)P(E/E2)) = (3/4 x 1)/(3/4 x 1 + 1/4 x 1/4) = (3/4)/(3/4 + 1/16) = (12/16)/(12 + 1)/16 = 12/13 |
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| 1063. |
Of the students in a college, it is known that 60% reside in hostel and 40% are day scholars (not residing in hostel). Previous year results report that 30% of all students who reside in hostel attain A grade and 20% of day scholars attain A grade in their annual examination. At the end of the year, one student is chosen at random from the college and he has an A grade, what is the probability that the student is a hosteler? |
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Answer» Let E1 : the event that the student is residing in hostel and E2 : the event that the student is not residing in the hostel. Let E : a student attains A grade, Then, E1 and E2 are mutually exclusive and exhaustive. Moreover, P(E1) = 60% = 60/100 = 3/5 and P(E2) = 40% = 40/100 = 2/5 Then P(E/E1) = 30% = 30/100 = 3/10 and P(E/E2) = 20% = 20/100 = 2/10 By using Baye’s theorem, we obtain P(E1/E) = (P(E1)P(E/E1))/(P(E1)P(E/E1) + P(E2)P(E/E2)) = (3/5 x 3/10)/(3/5 x 3/10 + 2/5 x 2/10) = 9/(9 + 4) = 9/13 |
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| 1064. |
Given P(A) = 3/5 and P(B) = 1/5. Find P(A or B), if A and B are mutually exclusive events. |
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Answer» Here, P(A) = 3/5, P(B) = 1/5 For mutually exclusive events A and B, P(A or B) = P(A) + P(B) ∴ P(A or B) = 3/5 + 1/5 = 4/5 |
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| 1065. |
(i) If P(A) = 1/3,P(B) = 1/5,P(A ∩ B) = 1/15, find P(A ∪ B) |
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Answer» (i) We have, P( A ∪ B) = P(A) + P(B) – P(A ∩ B) = 1/3 + 1/5 - 1/15 = (5 + 3 - 1)/15 = 7/15 |
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| 1066. |
If 2/11 is the probability of an event A, what is the probability of the event ‘not A’. |
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Answer» Given that P(A) = 2/11 if A is an event. To find: P (‘not A’) = P(A’) Since P(A’) = 1 – P(A) = 1 - 2/11 = 9/11 |
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| 1067. |
A letter is chosen at random from the word ‘ASSASSINATION’. Find the probability that letter is (i) a vowel (ii) a consonant. |
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Answer» In the word ASSASSINATION,we have A – 3 ; S – 4; I – 2; N – 2, O – 1 and T- 1. Total number of letters = 13. Among them, the vowels are: A – 3, I – 2, 0 – 1 is vowels are 6 in number. The consonants are: S – 4 ; N – 2, T-1. i.e., co-consonants are 7 in number. (i) P (a vowel) = 6/13 (ii) P (a consonant) = 7/13 |
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| 1068. |
Check whether the following probabilities P(A) and P(B) are consistently defined, (i) P(A) = 0.5, P(B) = 0.7, P(A∩B) = 0.6 (ii) P(A) = 0.5, P(B) = 0.4, P(A ∪ P) = 0.8 Note: P(A) and P(B) P(A ∩ B) are consistently defined iff P(A∩B) ≤ P(A) and P(B) |
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Answer» (i) P(A) = 0.6 and P(B) = 0.7 and P(A ∩ B) = 0.6 Here, p(A n B) > P(A) and P(A ∩ B)< P(B) P(A ∩ B) is not less than or equal to P(A) and P(B) ∴ P(A) and P(B), P(A n B) are not consistently defined. (ii) We have, P(A ∪ B) = P(A) + P(B) – p(A ∩ B) P(A ∩ B) = P(A) + P(B) – P(A ∪ B) = 0.5 + 0.5 – 0.8 = 0.9 – 0.8 = 0.1 ∴ P(A ∩ S) = 01 Here, P(A ∩ B) is less than P(A) and P(B) P(A) and P(B)P(A ∪ B) are consistently defined. (Note: P(A ∪ B)<P(A) + P(B)) |
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| 1069. |
Check whether the following probabilities P(A) and P(B) are consistently defined(i) P(A) = 0.5, P(B) = 0.7, P(A ∩ B) = 0.6(ii) P(A) = 0.5, P(B) = 0.4, P(A ∪ B) = 0.8 |
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Answer» (i) P(A) = 0.5, P(B) = 0.7, P(A ∩ B) = 0.6 Hence, P(A) and P(B) are consistently defined. |
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| 1070. |
Which of the following pairs of events is not mutually exclusive? (a) Throwing a number greater than 4 with a dice/ Throwing a number less than 4 with a dice. (b) Drawing a red card from a pack of cards /Draw a club from a pack of cards. (c) Drawing a diamond from a pack of cards/ Drawing an ace from a pack of cards. (d) Drawing a vowel card from a set of alphabet cards/Drawing a consonant card from a set of alphabet cards. |
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Answer» (c) Drawing a diamond from a pack of cards/ Drawing an ace from a pack of cards As we have an ace of diamonds, so drawing a diamond from a pack of cards also includes the possibility of drawing an ace. Hence the events are not mutually exclusive. |
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| 1071. |
In a lottery, a person chooses six different numbers at random from 1 to 20. If these six numbers match with the six numbers already fixed by the lottery committee, he wins the prize. What is the probability of winning the prize in the game? |
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Answer» All numbers are different (given in question), this will be the same as picking r different objects from n objects which is ncr Here, n= 20 and r = 6(as we have to pick 6 different objects from 20 objects) Now we shall calculate the value of 20C6 = \(\frac{(20)!}{(20-6)!\times(6)!}\)as nCr = \(\frac{(n)!}{(n-r)!\times(r)!}\) i.e. 20C6 = 38760 Therefore, 38760 cases are possible, and in that only one them has prize, i.e. total no. of desired outcome is 1 As we know, Probability of occurrence of an event = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) Therefore, the probability of winning a prize is = \(\frac{1}{38760}\) Conclusion: Probability of winning the prize in the game is \(\frac{1}{38760}\) |
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| 1072. |
In a lottery, a person chooses six different numbers at random from 1 to 20, and if these six numbers match with six numbers already fixed by the lottery committee, he wins the prize. What is the probability of winning the prize in the game? |
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Answer» given: six numbers are chosen from 1-20 Formula: P(E) = \(\frac{favorable\ outcomes}{total\ possible\ outcomes}\) we have to find the probability of winning the prize total possible outcomes of selecting six numbers from 1-20 is 20C6 therefore n(S)= 20C6 = 38760 let E be the event that all six numbers match with the given number (as winning number is fixed) n(E)=1 probability of occurrence of the event is P(E) = \(\frac{n(E)}{n(S)}\) P(E) = \(\frac{1}{38760}\) |
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| 1073. |
A, B and C are events associated with a random experiment such that P(A) = 0.3, P(B) = 0.4, P(C) = 0.8, P(A ∩ B) = 0.88, P(A ∩ C) = 0.48 and P(A ∩ B ∩ C) = 0.09. If P(A ∪ B ∪ C) ≥ 0.75, then prove that P(B ∩ C) lies in the interval [0.23, 0.48]. |
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Answer» Given, P(A) = 0.3, P(B) = 0.4, P(C) = 0.8 P(A ∩ B) = 0.08, P(A ∩ C) = 0.48, P(A ∩ B ∩ C) = 0. 09. We know– P(A ∪ B ∪ C) = P(A) + P(B) + P(C) – P(A ∩ B) – P(B ∩ C) – P(A ∩ C) + P(A ∩ B ∩ C) = 0.3 + 0.4 + 0.8 – 0.88 – p(B ∩ C) – 0.48 + 0.09 = 0.23 – p(B ∩ C) Since 0 ≤ P(A ∪ B ∪ C) ≤ and P(A ∪ B ∪ C) ≥ 0.75 ∴ P(B ∩ C) ≤ 0.48 and P(B ∩ C) ≥ 0.23 ∴ P(B ∩ C) lies in the interval [0.23, 0.48] |
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| 1074. |
A die is thrown. Find the probability of getting a 2 or a 3 |
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Answer» We know that, Probability of occurrence of an event = \(\frac{Total\,no. of\,Desired\,outcomes}{Total\,no. of\,outcomes}\) Total outcomes are 1, 2, 3, 4, 5, 6, and the desired outcomes are 2, 3 Therefore, total no. of outcomes are 6, and total no. of desired outcomes are 2 Probability of getting a 2 or 3 = \(\frac{2}{6}\) = \(\frac{1}{3}\) Conclusion: Probability of getting 2 or 3 when a die is thrown is \(\frac{1}{3}\) |
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| 1075. |
When a dice is rolled the probability of getting a composite number isA) 1/3B) 1/4C) 1/2D) 1/6 |
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Answer» Correct option is: A) \(\frac{1}{3}\) When a dice is rolled, then possible outcomes are {1, 2, 3, 4, 5, 6} Total No of outcomes is n (S) = 6 Composite numbers from 1 to 6 are {4, 6} Total No of composite numbers from 1 to 6 is 2 \(\therefore\) Probability of getting a composite number = \(\frac {Total \,No\, of \,composite \,number}{Total \, No \, of\, Possible \, outcomes}\) = \(\frac 26 = \frac 13\) Correct option is: A) \(\frac{1}{3}\) |
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| 1076. |
A die is thrown. Find the probability of getting an odd number |
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Answer» We know that, Probability of occurrence of an event = \(\frac{Total\,no. of\,Desired\,outcomes}{Total\,no. of\,outcomes}\) As 1, 3, 5 are odd numbers up to 6, so the desired outcomes are 1, 3, 5, and total outcomes are 1, 2, 3, 4, 5, 6 Therefore, total no. of outcomes are 6, and total no. of desired outcomes are 3 Probability of getting an odd number = \(\frac{3}{6}\) = \(\frac{1}{2}\) Conclusion: Probability of getting an odd number when a die is thrown is \(\frac{1}{2}\) |
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| 1077. |
Find the probability of almost two tails or almost two heads in a toss of three coins. |
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Answer» When we toss three coins, the sample space is– S = {HHH, HHT, HTH, HTT, THH, TTH, TTT} ⇒ n(S) = 8. Let ‘A’ and ‘B’ be the event of getting almost two tails and atmost two heads respectively. ∴ A = {HHH, HHT, HTH, HTT. THH, THT, TTH} ⇒ n(A) = 7 and B = {HHT, HTH, HTT, THH, THT, TTH, TTT} ⇒ n(B) = 7 A ∩ B = {HHT, HTH, HTT, THH, THT, TTH) ⇒ n(A ∩ B) = 6 ∴ P(A) = \(\frac{n(A)}{n(S)}= \frac{7}{8}\), P(B) = \(\frac{n(B)}{n(S)}= \frac{7}{8}\) P(A ∩ B) = \(\frac{n(A∩B)}{n(S)}=\frac{6}{8}\) We know– P(A ∪ B) = P(A) + P(B): P(A ∪ B) = \(\frac{7}{8}+\frac{7}{8}- \frac{6}{8}\) = \(\frac{8}{8}\) = 1. |
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| 1078. |
In a simultaneous toss of two coins, the probability of at least one head isA) 1/4B) 3/4C) 2/4D) 1/3 |
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Answer» Correct option is: B)\(\frac 34\) When two coins are tossed simultaneously, then total possible outcomes are {HH, HT, TH, TT} \(\therefore\) Total No of possible outcomes is n (S) = 4. Fabourable outcomes to event of getting at least one head are {HH, HT, TH}. \(\therefore\) Total No of favourable outcomes = 3 \(\therefore\) Probability of getting at least one head = \(\frac {Total \,No\, of \,favourable \,outcomes}{Total \,Possible \, outcomes}\) = \(\frac 34\) Correct option is: B) \(\frac{3}{4}\) |
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| 1079. |
An electronic machine chooses random numbers from 1 to 30. What is the probability that the number chosen is a triangular number? (a) \(\frac{11}{30}\) (b) \(\frac{1}{10}\)(c) \(\frac{1}{6}\)(d) \(\frac{7}{30}\) |
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Answer» (d) \(\frac{7}{30}\) Triangular numbers between 1 and 30 are 1, 3, 6, 10, 15, 21, 27, i.e., 7 in number. \(\therefore\) Reqd. probability = \(\frac{7}{30}\) |
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| 1080. |
In a simultaneous toss of two coins, find the probability of getting two tails. (a) \(\frac{1}{2}\)(b) \(\frac{1}{4}\) (c) \(\frac{3}{4}\)(d) \(\frac{1}{3}\) |
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Answer» (b) \(\frac{1}{4}\) The sample space for a simultaneous toss of two coins is S = { HH, HT, TH, TT} Favourable cases = {TT} \(\therefore\) P ( getting two tails ) =\(\frac{1}{4}\) |
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| 1081. |
A bag contains 4 blue, 5 red and 7 green balls. If 4 balls are drawn one by one with replacement, what is the probability that all are blue?(a) \(\frac{1}{16}\)(b) \(\frac{1}{4}\)(c) \(\frac{1}{256}\)(d) \(\frac{1}{64}\) |
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Answer» (c) \(\frac{1}{256}\) Probability of drawing a blue ball = \(\frac{4}{4+5+7}\) = \(\frac{4}{16}\)= \(\frac{1}{4}\) \(\therefore\) Required probability = \(\frac{1}{4}\) x \(\frac{1}{4}\) x \(\frac{1}{4}\) x \(\frac{1}{4}\) = \(\frac{1}{256}\). |
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| 1082. |
A die is thrown. Find the probability of getting a prime number |
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Answer» We know that, Probability of occurrence of an event = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) As 2, 3, 5 are prime numbers up to 6, so the desired outcomes are 2, 3, 5, and total outcomes are 1, 2, 3, 4, 5, 6 Therefore, total no. of outcomes are 6, and total no. of desired outcomes are 3 Probability of getting a prime number = \(\frac{3}{6}\) = \(\frac{1}{2}\) Conclusion: Probability of getting a prime number when a die is thrown is \(\frac{1}{2}\) |
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| 1083. |
Three coins are tossed simultaneously. Find the probability of at least one head and one tail.(a) \(\frac{1}{2}\)(b) \(\frac{1}{4}\)(c) \(\frac{3}{4}\)(d) None of these |
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Answer» (c) \(\frac{3}{4}\) The sample space for a simultaneous toss of three coins S = {HHH, HHT, HTT, THH,TTH, THT, HTH, HHH} Favourable cases = {HHT, HTT, THH, TTH, THT, HTH} \(\therefore\) P ( getting at least one head, one tail) =\(\frac{6}{8}\) =\(\frac{3}{4}\). |
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| 1084. |
In a single throw of three dice, find the probability of getting a total of 17 or 18 |
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Answer» Given: three dices are thrown Formula: P(E) = \(\frac{favourable \ outcomes}{total \ possible \ outcomes}\) Total number of possible outcomes are 63=216 Therefore n(S)=216 Let E be the event of getting total of 17 or 18 E= {(6,6,5) (6,5,6) (5,6,6) (6,6,6)} n(E)=4 P(E) = \(\frac{n(E)}{n(S)}\) P(E) = \(\frac{4}{216}\) = \(\frac{1}{54}\) |
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| 1085. |
A bag contains 12 balls of two different colours, out of which x are white. One ball is drawn at random. If 6 more white balls are put in the bag, the probability of drawing a white ball now will be double to that of the previous probability of drawing a white ball. Then, the value of x is .... (A) 3 (B) 4 (C) 5 (D) 6 |
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Answer» The correct option is: (A) 3 Explanation: If is given that, total number of balls = 12 Number of white balls = x .'. Probability of getting a white ball = x/12 Now, 6 white balls are added. .'. Total number of balls = 12 + 6 = 18 Number of white balls = x + 6 .'. Probability of getting a white ball = x + 6/18 According to the question, (x + 6)/18 = 2 x x/12 => x + 6 = 3x => x = 3 .'. Number of white balls = 3 |
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| 1086. |
A bag contains 4 white and 5 black balls. A ball is drawn at random from the bag. Find the probability that the ball is drawn is white. |
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Answer» We know that, Probability of occurrence of an event = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) By permutation and combination, total no. of ways to pick r objects from given n objects is nCr Now, total no. of ways to pick a ball from 9 balls is 9c1 = 9 Our desired output is to pick a white ball. So, no. of ways to pick a white ball from 4 white balls (because the white ball can be picked from only white balls) is 4c1 = 4 Therefore, the probability of picking a white ball = \(\frac{4}{9}\) Conclusion: Probability of picking a white ball from 4 white balls and 5 white balls is \(\frac{4}{9}\) |
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| 1087. |
In a single throw of two dice, what is the probability of getting a total of 11.(a) \(\frac{1}{9}\)(b) \(\frac{1}{18}\)(c) \(\frac{1}{12}\)(d) \(\frac{35}{36}\) |
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Answer» (b) \(\frac{1}{18}\) Total number of exhaustive cases = 6 × 6 = 36 A total of 11 may be obtained in 2 ways as (5, 6), (6, 5). \(\therefore\) P (total of 11) = \(\frac{2}{36}\)=\(\frac{1}{18}\). |
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| 1088. |
Fill in the blanks. (i) In a single throw of a dice, the probability of getting a number greater than 2 is P.(ii) A card is drawn from a deck of 52 cards. The probability of drawing a red card is Q and a face card is P. (iii) A bag contains 2 blue and 3 green marbles, then the probability of drawing red marble S . |
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Answer» The correct option is: (C) Explanation: (i) Total number of outcomes = 6 Numbers greater than 2 are 3,4, 5, and 6. Favorable outcomes = 4 .'. Required probability = 4/6 = 2/3 (ii) Total number of outcomes = 52 Number of red cards = 26 .'. Probability of drawing a red card = 26/52 = 1/2 Number of face cards = 12 .'. Probability of drawing a face card = 12/52 = 3/13 (iii) Since, there is no red marble in the bag, so probability of drawing a red marble is zero. |
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| 1089. |
A die is thrown. Find the probability of getting a multiple of 3 |
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Answer» We know that, Probability of occurrence of an event = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) As 3, 6 are multiples up to 6, so the desired outcomes are 3, 6, and total outcomes are 1, 2, 3, 4, 5, 6 Therefore, total no. of outcomes are 6, and total no. of desired outcomes are 2 Probability of getting multiple of 3 = \(\frac{2}{6}\) = \(\frac{1}{3}\) Conclusion: Probability of getting multiple of 3 when die is thrown is \(\frac{1}{3}\) |
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| 1090. |
In a single throw of two dice, find P (a total of 9 or 11) |
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Answer» We know that, Probability of occurrence of an event = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) Total outcomes are (1, 1), (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (2, 1), (2, 2), (2, 3), (2, 4), (2, 5), (2, 6), (3, 1), (3, 2), (3, 3), (3, 4), (3, 5), (3, 6), (4, 1), (4, 2), (4, 3), (4, 4), (4, 5), (4, 6) , (5, 1), (5, 2), (5, 3), (5, 4), (5, 5), (5, 6) , (6, 1), (6, 2), (6, 3), (6, 4), (6, 5), (6, 6) Desired outcomes are (3, 6), (4, 5), (5, 4), (6, 3), (6, 5) , (5, 6) Total no. of outcomes are 36 and desired outcomes are 6 Therefore, probability of getting total equal to 9 or 11 = \(\frac{6}{36}\) = \(\frac{1}{6}\) Conclusion: Probability of getting total equal to 9 or 11, when two dice are rolled is \(\frac{1}{6}\) |
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| 1091. |
A die is thrown. Find the probability of getting a number between 3 and 6 |
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Answer» We know that, Probability of occurrence of an event = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) As 4, 5 are two numbers between 3 and, so the desired outcomes are 3, 6, and total outcomes are 1, 2, 3, 4, 5, 6 Therefore, total no. of outcomes are 6, and total no.of desired outcomes are 2 Probability of getting a number between 3 and 6 = \(\frac{2}{6}\) = \(\frac{1}{3}\) Conclusion: Probability of getting a number between 3 and 6 when a die is thrown is \(\frac{1}{3}\) |
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| 1092. |
In a single throw of two dice, find P (a total greater than 8) |
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Answer» We know that, Probability of occurrence of an event = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) Total outcomes are (1, 1), (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (2, 1), (2, 2), (2, 3), (2, 4), (2, 5), (2, 6), (3, 1), (3, 2), (3, 3), (3, 4), (3, 5), (3, 6), (4, 1), (4, 2), (4, 3), (4, 4), (4, 5), (4, 6) , (5, 1), (5, 2), (5, 3), (5, 4), (5, 5), (5, 6) , (6, 1), (6, 2), (6, 3), (6, 4), (6, 5), (6, 6) Desired outcomes are (3, 6), (4, 5), (4, 6), (5, 4), (5, 5), (5, 6), (6, 3), (6, 4), (6, 5), (6, 6) Total no. of outcomes are 36 and desired outcomes are 10 Therefore, probability of getting total greater than 8 = \(\frac{10}{36}\) = \(\frac{5}{18}\) Conclusion: Probability of getting total greater than 8, when two dice are rolled is \(\frac{5}{18}\) |
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| 1093. |
In a single throw of two dice, find the probability of (i) getting a sum less than 6 (ii) getting a doublet of odd numbers (iii) getting the sum as a prime number |
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Answer» (i) We know that, Probability of occurrence of an event = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) Outcomes are (1, 1), (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (2, 1), (2, 2), (2, 3), (2, 4), (2, 5), (2, 6), (3, 1), (3, 2), (3, 3), (3, 4), (3, 5), (3, 6), (4, 1), (4, 2), (4, 3), (4, 4), (4, 5), (4, 6) , (5, 1), (5, 2), (5, 3), (5, 4), (5, 5), (5, 6) , (6, 1), (6, 2), (6, 3), (6, 4), (6, 5), (6, 6) Total no. of outcomes are 36 In that only (1, 1), (1, 2), (1, 3), (1, 4), (2, 1), (2, 2), (2, 3), (3, 1), (3, 2), (4, 1) are our desired outputs as there sum is less than 6 Therefore no. of desired outcomes are 10 Therefore, the probability of getting a sum less than 6 = \(\frac{10}{36}\) = \(\frac{5}{18}\) Conclusion: Probability of getting a sum less than 6, when two dice are rolled is \(\frac{5}{18}\) (ii) We know that, Probability of occurrence of an event = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) In (a, b) if a=b then it is called a doublet Total doublets are (1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6) In (a, b) if a=b and if a, b both are odd then it is called a doublet Odd doublets are (1, 1), (3, 3), (5, 5) Outcomes are (1, 1), (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (2, 1), (2, 2), (2, 3), (2, 4), (2, 5), (2, 6), (3, 1), (3, 2), (3, 3), (3, 4), (3, 5), (3, 6), (4, 1), (4, 2), (4, 3), (4, 4), (4, 5), (4, 6) , (5, 1), (5, 2), (5, 3), (5, 4), (5, 5), (5, 6) , (6, 1), (6, 2), (6, 3), (6, 4), (6, 5), (6, 6) Total no. of outcomes are 36 and desired outcomes are 3 Therefore, probability of getting doublet of odd numbers = \(\frac{3}{36}\) = \(\frac{1}{12}\) Conclusion: Probability of getting doublet of odd numbers, when two dice are rolled is \(\frac{1}{12}\) (iii) We know that, Probability of occurrence of an event = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) Outcomes are (1, 1), (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (2, 1), (2, 2), (2, 3), (2, 4), (2, 5), (2, 6), (3, 1), (3, 2), (3, 3), (3, 4), (3, 5), (3, 6), (4, 1), (4, 2), (4, 3), (4, 4), (4, 5), (4, 6) , (5, 1), (5, 2), (5, 3), (5, 4), (5, 5), (5, 6) , (6, 1), (6, 2), (6, 3), (6, 4), (6, 5), (6, 6) Total no. of outcomes are 36 Desired outputs are (1, 1), (1, 2), (1, 4), (1, 6), (2, 1), (2, 3), (2, 5), (3, 2), (3, 4), (4, 1), (4, 3), (5, 2), (5, 6), (6, 1), (6, 5) Total no. of desired outputs are 15 Therefore, probability of getting the sum as a prime number = \(\frac{15}{36}\) = \(\frac{5}{12}\) Conclusion: Probability of getting the sum as a prime number, when two dice are rolled is \(\frac{5}{12}\) |
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| 1094. |
In a single throw of two dice, find P (a total of 10) |
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Answer» We know that, Probability of occurrence of an event = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) Total outcomes are (1, 1), (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (2, 1), (2, 2), (2, 3), (2, 4), (2, 5), (2, 6), (3, 1), (3, 2), (3, 3), (3, 4), (3, 5), (3, 6), (4, 1), (4, 2), (4, 3), (4, 4), (4, 5), (4, 6) , (5, 1), (5, 2), (5, 3), (5, 4), (5, 5), (5, 6) , (6, 1), (6, 2), (6, 3), (6, 4), (6, 5), (6, 6) Desired outcomes are (4, 6), (5, 5), (6, 4) Total no. of outcomes are 36 and desired outcomes are 3 Therefore, the probability of getting a total of 10 = \(\frac{3}{36}\) = \(\frac{1}{12}\) Conclusion: Probability of getting total sum 10, when two dice are rolled is \(\frac{1}{12}\) |
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| 1095. |
In a single throw of two dice, find P (a number greater than 3 on each die) |
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Answer» We know that, Probability of occurrence of an event = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) Total outcomes are (1, 1), (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (2, 1), (2, 2), (2, 3), (2, 4), (2, 5), (2, 6), (3, 1), (3, 2), (3, 3), (3, 4), (3, 5), (3, 6), (4, 1), (4, 2), (4, 3), (4, 4), (4, 5), (4, 6) , (5, 1), (5, 2), (5, 3), (5, 4), (5, 5), (5, 6) , (6, 1), (6, 2), (6, 3), (6, 4), (6, 5), (6, 6) Desired outcomes are (4, 4), (4, 5), (4, 6), (5, 4), (5, 5), (5, 6), (6, 4), (6, 5), (6, 6) Total no. of outcomes are 36 and desired outcomes are 9 Therefore, probability of getting number greater than 3 on each die = \(\frac{9}{36}\) = \(\frac{1}{4}\) Conclusion: Probability of getting a number greater than 3 on each die, when two dice are rolled is \(\frac{1}{4}\) |
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| 1096. |
In a single throw of two dice, find P (an odd number on the first die and a 6 on the second) |
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Answer» We know that, Probability of occurrence of an event = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) Total outcomes are (1, 1), (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (2, 1), (2, 2), (2, 3), (2, 4), (2, 5), (2, 6), (3, 1), (3, 2), (3, 3), (3, 4), (3, 5), (3, 6), (4, 1), (4, 2), (4, 3), (4, 4), (4, 5), (4, 6) , (5, 1), (5, 2), (5, 3), (5, 4), (5, 5), (5, 6) , (6, 1), (6, 2), (6, 3), (6, 4), (6, 5), (6, 6) Desired outcomes are (1, 6), (3, 6), (5, 6) Total no. of outcomes are 36 and desired outcomes are 3 Therefore, probability of getting odd on the first die and 6 on the second die = \(\frac{3}{36}\) = \(\frac{1}{12}\) Conclusion: Probability of getting odd on the first die and 6 on the second die, when two dice are rolled is \(\frac{1}{12}\) |
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| 1097. |
If P(B) = 0.5 and P(A ∩ B) = 0.32, then find p( A/B). |
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Answer» P(A/B) = P(A ∩ B)/P(B) = 0.32/0.5 = 32/50 = 16/25 |
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| 1098. |
Three unbiased coins are tossed once. Find the probability of getting exactly one tail |
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Answer» We know that, Probability of occurrence of an event = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) Let T be tails and H be heads Total possible outcomes = TTT, TTH, THT, HTT, THH, HTH, HHT, HHH Desired outcomes are exactly one tail. So, desired outputs are THH, HTH, HHT Total no. of outcomes are 8 and desired outcomes are 3 Therefore, the probability of getting exactly one tail = \(\frac{3}{8}\) Conclusion: Probability of getting exactly one tail is \(\frac{3}{8}\) |
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| 1099. |
If six students, including two particular students A and B, stand in a row, then the probability that A and B are separated with one student in between them isA. `8//15`B. `1//5`C. `2//15`D. `4//15` |
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Answer» Correct Answer - D Total number of ways in which 6 students can stand in row is 6!. One student can stand between A and B in `.^(4)C_(1)xx2!` ways. Considering these three as one individual we have 4 students who can stand in a row in 4! Ways. Therefore, number of ways in which one student is there between A and B and is `.^(4)C_(1)xx2!xx4!`. Hence, required probability `=(.^(4)C_(1)xx2!xx4!)/(6!)=(4)/(5)` |
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| 1100. |
The minimum number of times a fair coin needs to be tossed, so that the probability of getting at least two heads is at least 0.96 is :A. 7B. 9C. 8D. 5 |
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Answer» Correct Answer - C Let the coin be tossed n times and let X-denote the number of heads in n tosses of the coin. Then, `therefore P(X=r)= .^(n)C_(r )((1)/(2))^(r )((1)/(2))^(n-r) = .^(n)C_(r )((1)/(2))^(n), r=0,1,2,..,n` It is given that `P(X ge 2) ge 0.96` `implies underset(r=2)overset(n)(sum)P(X=r) ge 0.96` `implies underset(r=2)overset(n)(sum) .^(n)C_(r )((1)/(2))^(n) ge 0.96` `implies (1)/(2^(n))( underset(r=2)overset(n)(sum) .^(n)C_(r )) ge 0.96` `implies (1)/(2^(n)) (2^(n) - .^(n)C_(0) - .^(n)C_(1)) ge 0.96` `implies 1-(n+1)/(2^(n)) ge 0.96` `implies (n+1) le (0.04) 2^(n)` `implies n=8, 9, 10,`.. |
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