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901.

"If " `P(AcupB)=P(AcapB)`" for any two events A and B, then"`A. `P(A)=P(B)`B. `P(A)gtP(B)`C. `P(A)ltP(B)`D. None of these

Answer» Correct Answer - A
(a) `"Given " P(AcupB)=P(AcapB)`
`P(A)+P(B)-P(AcapB)=P(AcapB)`
`rArr " "[P(A)-P(AcapB)]+[P(B)-P(AcapB)]=0`
`"But" " "P(A)-P(AcapB)ge=0`
`"and" " "P(B)-P(AcapB)ge=0" "[becauseP(AcapB)leP(A)or P(B)]`
`rArr " "P(A)-P(AcapB)=0`
`and " "P(B)-P(AcapB)=0`
`["since, sum of two non-negative numbers can be zero only when these numbers aree zero"]`
`rArr " "P(A)=P(AcapB)`
`and " "P(B)=P(AcapB)`
`therefore " "P(A)=P(B)`
902.

If P(A)=`4/5` and P(`AcapB`)=`7/10`, then `P(B//A)` is equal toA. `1/10`B. `1/8`C. `7/8`D. `17/20`

Answer» `because P(A)=4/5,P(Acap)=7/10`
`thereforeP(B//A)=(P(AcapB))/(P(A))=(7//10)/(4//5)=7/8`
903.

If P(A)=0.4,P(B)=0.8 and P(B/A)=0.6, then `P(AcupB)` is equal toA. 0.24B. 0.3C. 0.48D. 0.96

Answer» Here, P(A)=0.4,P(B)=0.8andP(A/B)=0.6
`because P(B//A)=(P(BcapA))/(P(A))`
`rArr P(BcapA)=P(B//A)cdotP(A)`
`=0.6xx0.4=0.24`
`thereforeP(AcupB)=P(A)+P(B)-P(AcapB)`
`=0.4+0.8-0.24`
`=1.2-0.24=0.96`
904.

If `P(AcapB)=7/10 and P(B)=17/20`,then P(A/B) equals toA. `14/17`B. `17/20`C. `7/8`D. `1/8`

Answer» Here `P(capB)=7/10and P(B)=17/20`
`thereforeP(A//B)=(P(AcapB))/(P(B))=(7//10)/(14//17)`
905.

If two events are independent, thenA. they must be mutually exclusiveB. the sum of their probabilities must be equal to 1C. Both (a) and (b) are correctD. none of the above is correct

Answer» If two events A and B are independent, then we knpw that
`P(AcapB)=P(A)cdotP(B),P(A)ne0,P(B)ne0`
`Since,m a nd B have a common outcome
Further, mutually exlusive events never have a common outcome.
In other words, two independent eevnts having non-zeroprobabilities of occurrence cannot be mutuallyexclusive events having non-zero probabilitiesof outcome cannot be independent.
906.

If A and B are two events such that `P(AcupB)=(5)/(6), P(A)=(1)/(3) and P(B)=(3)/(4)`, then A and B areA. mutually exclusiveB. dependentC. independentD. None of these

Answer» Correct Answer - (c)
907.

If A and B are two events such that `P(AcupB)=(3)/(4), P(AcapB)=(1)/(4), P(overline(A))=(2)/(3), then P(overline(A)cupB)` is equal toA. `(11)/(12)`B. `(3)/(8)`C. `(5)/(8)`D. `(1)/(4)`

Answer» Correct Answer - (a)
908.

If `(A)=3/10,P(B)=2/5 and P(AcupB)=3/5` then P(B/A)+P(A/B) equals toA. `1/4`B. `1/3`C. `5/12`D. `7/12`

Answer» Here, `P(A)=3/10,P(B)=2/5andP(AcupB)=3/5`
`P(B//A)+P(A//B)=(P(BcapA))/(P(A))+(P(AcapB))/(P(B))`
`=(P(A)+P(B)-P(AcupB))/(P(A))`+`=(P(A)+P(B)-P(AcupB))/(P(B))`
`[{:(becauseP(AcupB)=P(A)+P(B)-P(AcapB)),("i.e.,"P(AcapB)=P(A)+P(B)-P(AcupB)):}]`
`=(3/10+2/5-3/5)/(3/10)+(3/10+2/5-3/5)/(2/5)`
`=(1/10)/(3/10)+(1/10)/(2/5)=1/3+1/4=7/12`
909.

If A and B are two events such that `P(B)=3/5,P(A//B)=1/2` and `P(AcupB)=4/5`, then P(A) equals toA. `3/10`B. `1/5`C. `1/2`D. `3/5`

Answer» Here,P(B)=`3/5`,P(A/B)=1/2and P(`AcupB`)=4/5
`becauseP(A//B)=(P(AcapB))/(P(B))`
`rArr1/2=(P(AcapB))/(3//5)`
`rArrP(AcapB)=3/5xx1/2=3/10`
and `P(AcupB)=P(A)+P(B)-P(AcapB)`
`rArr4/5=P(A)+3/5-3/10`
`thereforeP(A)=4/5-3/5+3/10=(8-6+3)/10=1/2`
910.

Let A and B be two events such that `Poverline((AcupB))=(1)/(6),P(AcapB)=(1)/(4) and P(overline(A))=(1)/(4)`,where `overline(A)` stands for complement of event A. then , events A and B areA. independent but not equally likelyB. independent and equally likelyC. mutually exclusive and independentD. equally likely but not independent

Answer» Correct Answer - A
911.

A bag contains 4 white ball, 6 red balls, 7 black balls and 3 blue balls. One ball is drawn at random from the bag. Find the probability that the ball drawn is (i) white (ii) not black (iii) neither white nor black

Answer»

Total number of balls = 20

(i) Number of White Balls = 4

Total Balls = 20

P(white) = 4/20 = 1/5

(ii) No black means the we have to pick white, red, blue balls only

P(not black) = 13/20

(iii) neither black nor white means only white and red balls are left

P(neither white nor black) = 9/20

912.

12 balls are keeped in three bags. The probability that there are 3 balls in first bag is:A. `110/9(2/3)^(10)`B. `110/9(3/2)^(10)`C. `(.^(12)C_(3))/(3^(12))`D. `(.^(12)C_(3))/(12^(3))`

Answer» Correct Answer - A
N/a
913.

According to a meteorological report for 300 consecutive days in a year , its weather forecasts were correct 180 times . Out of these days , one day is chosen at random . What is the probability that the weather forecast was (i) correct on that day ? (ii) not correct on that day ?

Answer» Total number of days = 300.
(i) Let E = event that the forecast was correct on the chosen day . Then ,
`P(E) = ("no., of days for which the forecasts were correct")/("total number of days")`
`= (180)/(300) = (3)/(5) = 0.6`.
(ii) Number of days on which the forecast was not correct
= 300 - 180 = 120 .
Let F = event that the forecast was not correct on the given day .
Then , P(F) = `(120)/(300) = (2)/(5) = 0.4.`
914.

In a circket match , a batsman hits the boundary 5 times out of 40 balls played by him . Find the probability that the boundary is not hit by the ball.

Answer» Total number of balls thrown = 40 .
Number of times , the boundary is hit by the ball = 5.
Number of times , the boundary is not hit by the ball = 40 - 5
= 35 .
Let E be the event that the boundary is not hit by the ball.
Then ,
`P(E) = ("number of times the boundary is not hit by the ball")/("total number of balls thrown")`
= `(35)/(40) = (7)/(8)`.
915.

A survey of 250 girls of a school was conducted and it was found that 105 girls like tea while 145 dislike it . Out of these girls , one girl is selected at random . What is the probability that the selected girl (i) likes tea , (ii) does not like tea ?

Answer» Total number of girls = 250 .
Number of girls who like tea = 105.
Number of girls who dislike tea = 145.
(i) Let `E_(1)` = event that the selected girl likes tea . Then .
P(selected girl like tea)

= `P(E_(1)) = ("number of girls who like tea")/("total number of girls") = (105)/(250) = 0.42`
(ii) `E_(2)` = event that the selected girl dislikes tea . Then ,
P(selected girl dislikes tea)
= `P (E_(2)) = ("number of girls who dislikes tea")/("total number of girls") = (145)/(250) = 0.58` .
916.

One card is drawn at random from a well-shuffled deck of 52 cards. Find the probability that the card drawn is (i) a 4 (ii) a queen (iii) a black card.

Answer»

(i) Total number cards in a deck = 52 

Number of 4’s in a deck of cards = 4

Probability (P) = \(\frac{Number\,of\,favorable\,outcomes}{Total\,number\,of\,in\,a\,deck}\)

∴ Probability of drawing a 4 numbered card from the deck of cards P(4)

\(\frac{Numbe\,of\,4's\,in\,deck\,of\,cards}{Total\,number\,of\,cards\,in\,a\,deck}\) = \(\frac{4}{52}=\frac{1}{13}\)

(ii) Total number cards in a deck = 52

Number of Queens in a deck of cards = 4

Probability (P) = \(\frac{Number\,of\,favorable\,outcomes}{Total\,number\,of\,in\,a\,deck}\)

∴ Probability of drawing a queen from the deck of cards P(queen)

\(\frac{Number\,of\,queen\,in\,a\,deck\,of\,cards}{Total\,number\,of\,in\,a\,deck}\) = \(\frac{4}{52}=\frac{1}{13}\)

(iii) Total number cards in a deck = 52 

Number of black cards in a deck of cards = 26 (13 spades and 13 clubs)

Probability (P) = \(\frac{Number\,of\,favorable\,outcomes}{Total\,number\,of\,in\,a\,deck}\)

∴ Probability of drawing a black card from the deck of cards P(black)

\(\frac{Number\,of\,black\,cards\,in\,a\,deck\,of\,cards}{Total\,number\,of\,cards\,in\,a\,deck}\) = \(\frac{26}{52}=\frac{1}{2}\)

917.

One card is drawn at random from a well-shuffled deck of 52 cards. Find the probability that the card drawn is (i) a king (ii) a spade (iii) a red queen (iv) a black 8.

Answer»

(i) Total number cards in a deck = 52 

Number of kings in a deck of cards = 4

Probability (P) = \(\frac{Number\,of\,favorable\,outcomes}{Total\,number\,of\,outcomes}\)

∴ Probability of drawing a king from the deck of cards P(king)

\(\frac{Number\,of\,kings\,in\,a\,deck\,of\,cards}{Total\,number\,of\,cards\,in\,a\,deck}\) = \(\frac{4}{52}=\frac{1}{13}\)

(ii) Total number cards in a deck = 52 

Number of spades in a deck of cards = 13

Probability (P) = \(\frac{Number\,of\,favorable\,outcomes}{Total\,number\,of\,outcomes}\)

∴ Probability of drawing a spade from the deck of cards P(spade)

\(\frac{Number\,of\,spades\,in\,a\,deck\,of\,cards}{Total\,number\,of\,cards\,in\,a\,deck}\) = \(\frac{13}{52}=\frac{1}{4}\)

(iii) Total number cards in a deck = 52

Chances of drawing a Red queen from the deck of cards = 2 (they are queen of hearts and queen of diamonds)

Probability (P) = \(\frac{Number\,of\,favorable\,outcomes}{Total\,number\,of\,outcomes}\)

∴ Probability of drawing a Red queen from the deck of cards P(Red queen)

\(\frac{chances\,drawing\,a\,red\,queen\,from\,the\,deck\,of\,cards}{Total\,number\,of\,cards\,in\,a\,deck}\) = \(\frac{2}{52}=\frac{1}{26}\)

(iv) Total number cards in a deck = 52 

Chances of drawing a black 8 from the deck of cards = 2 (they are 8 of clubs and 8 of spades)

Probability (P) = \(\frac{Number\,of\,favorable\,outcomes}{Total\,number\,of\,outcomes}\)

∴ Probability of drawing a black 8 from a deck of cards P(black 8)

\(\frac{chances\,drawing\,a\,black\,from\,from\,the\,deck\,of\,cards}{Total\,number\,of\,cards\,in\,a\,deck}\) = \(\frac{2}{52}=\frac{1}{26}\)

918.

A die is thrown at random. Find the probability of getting (i) 2 (ii) a number less than 3 (iii) a composite number (iv) a number not less than 4.

Answer»

(i) Total number of outcomes = 6 (they are 1,2,3,4,5,6) 

Chances of getting 2 on the die = 1

Probability (P) = \(\frac{Number\,of\,favorable\,outcomes}{Total\,number\,of\,outcomes}\)

∴ Probability of getting 2 on die P(2)

\(\frac{possible\,chances\,of\,getting\,2}{Total\,number\,of\,outcomes}\) = \(\frac{1}{6}\)

(ii) Total number of outcomes = 6 (they are 1,2,3,4,5,6) 

Chances of getting a number less than 3 on the die = 2 (They are 1,2)

Probability (P) = \(\frac{Number\,of\,favorable\,outcomes}{Total\,number\,of\,outcomes}\)

∴ Probability of getting a number less than 3 on die P(less than 3)

\(\frac{Possible\,chances\,of\,getting\,a\,number\,less\,than\,3}{Total\,number\,of\,outcomes}\) = \(\frac{2}{6}=\frac{1}{3}\)

(iii) Total number of outcomes = 6 (they are 1,2,3,4,5,6) 

Composite number: A number which is not a prime number or a number which is divisible by numbers other than 1 and the number itself. 

Chances of getting a composite number on the die = 2 (They are 4,6)

Probability (P) = \(\frac{Number\,of\,favorable\,outcomes}{Total\,number\,of\,outcomes}\)

∴ Probability of getting a composite number on die the P(composite number)

\(\frac{Possible\,chances\,of\,getting\,a\,number\,less\,than\,3}{Total\,number\,of\,outcomes}\) = \(\frac{2}{6}=\frac{1}{3}\)

(iv) Total number of outcomes = 6 (they are 1,2,3,4,5,6) 

Chances of getting a number not less than 4 on the die = 4 (They are 4,5,6)

Probability (P) = \(\frac{Number\,of\,favorable\,outcomes}{Total\,number\,of\,outcomes}\)

∴ Probability of getting a number not less than 4 on die P(not less than 4)

\(\frac{Possible\,chances\,of\,getting\,a\,number\,less\,than\,3}{Total\,number\,of\,outcomes}\) = \(\frac{3}{6}=\frac{1}{2}\)

919.

A box contains 19 balls bearing numbers 1, 2, 3 ..., 19 respectively. A ball is drawn at random from the box. Find the probability that the number on the ball is (i) a prime number (ii) an even number (iii) a number divisible by 3.

Answer»

(i) Total number of ball bearings = 19 

Chances of drawing a prime numbered ball = 9 (They are 2,3,5,7,11,13,17,19)

Probability (P) = \(\frac{Number\,of\,favorable\,outcomes}{Total\,number\,of\,outcomes}\)

∴ Probability of drawing a prime numbered ball bearing P(prime ball)

\(\frac{possible\,chances\,of\,drawing\,a\,prime\,numbered\,ball\,bearing}{Total\,number\,of\,ball\,bearings}\) = \(\frac{8}{19}\)

(ii) Total number of ball bearings = 19 

Chances of drawing an even numbered ball = 9 (They are 2,4,6,8,10,12,14,16,18)

Probability (P) = \(\frac{Number\,of\,favorable\,outcomes}{Total\,number\,of\,outcomes}\)

∴ Probability of drawing a prime numbered ball bearing P(prime ball)

\(\frac{possible\,chances\,of\,drawing\,a\,prime\,numbered\,ball\,bearing}{Total\,number\,of\,ball\,bearings}\) = \(\frac{9}{19}\)

(iii) Total number of ball bearings = 19 

Chances of drawing a numbered ball which is divisible by 3 = 6 (They are 3,6,9,12,15,18)

Probability (P) = \(\frac{Number\,of\,favorable\,outcomes}{Total\,number\,of\,outcomes}\)

∴ Probability of drawing a numbered ball bearing which is divisible by 3 P(ball divisible by 3)

\(\frac{possible\,chances\,of\,drawing\,a\,numbered\,which\,is\,divisible\,by\,3}{Total\,number\,of\,ball\,bearings}\) = \(\frac{6}{19}\)

920.

The sample space for a random experiment of selecting numbers is U = (1, 2, 3, …. 120} and all the outcomes in the sample space are equiprobable. Find the probability that the number selected is:(1) a multiple of 3(2) not a multiple of 3(3) a multiple of 4(4) not a multiple of 4(5) a multiple of both 3 and 4

Answer»

Here, U = {1, 2, 3, …, 120} ‘

A number is selected at random.

∴ Total number of primary outcomes is n = 120C1 = 120.

(1) A = Event that the number selected is a multiple of 3.

= {3, 6, 9, 12, …, 117, 120}

∴ Favourable outcomes for the event A is m = 40.

Hence, P(A) = \(\frac{m}{n} = \frac{40}{120} = \frac{1}{3}\)

(2) A’ = Event that the number selected is not a multiple of 3.

∴ P(A’) = 1 – P(A)

= \(1 – \frac{1}{3} = \frac{2}{3}\)

(3) B = Event that the number selected is a multiple of 4.

= {4, 8, 12, 16, …, 116, 120}

∴ Favourable outcomes for the event B is m = 30.

Hence, P(B) = \(\frac{m}{n} = \frac{30}{120} = \frac{1}{4}\)

(4) B’ = Event that the selected number is not a multiple of 4.

∴ P(B’) = 1 – P(B)

= 1 – \(\frac{1}{4} = \frac{3}{4}\)

(5) A ∩ B = Event that the number selected is a multiple of both 3 and 4, i.e., a multiple of 12.

∴ A ∩ B = {12, 24, 36, 48, …, 108, 120}

∴ Favourable outcomes for the event A ∩ B is m = 10.

Hence, P(A ∩ B) = \(\frac{m}{n} = \frac{10}{20} = \frac{1}{12}\)

921.

Two dice are thrown. The events A, B, C, D, E and F are describes as follows. A = Getting an even number on the first die. B. Getting an odd number on the first die. C = Getting at most 5 as sum of the numbers on the two dice. D = Getting the sum of the numbers on the dice greater than 5 but less than 10. E = Getting at least 10 as the sum of the numbers on the dice. F = Getting an odd number on one of the dice. (i) Describe the following events: A and B, B or C, B and C, A and E, A or F, A and F (ii) State true or false:(a) A and B are mutually exclusive.(b) A and B are mutually exclusive and exhaustive events (c) A and C are mutually exclusive events (d) C and D are mutually exclusive and exhaustive events (e) C, d and E are mutually exclusive and exhaustive events (f) A’ and B’ are mutually exclusive events (g) A, B, F are mutually exclusive and exhaustive events

Answer»

To Find: Describe the given events. 

Explanation: when two dice are thrown then the no. of possible outcomes are 62 = 36 

Now, According to the question, 

A = Getting an even number of the first die. 

A = {(2, 1)(2, 2)(2, 3)(2, 4)(2, 5)(2, 6)(4, 1)(4, 2)(4, 3)(4, 4)(6, 1)(6, 2)(6, 3)(6, 4)(6, 5)(6, 6)} 

B = Getting an odd number on the first dice 

B = {(1, 1) (1, 2) (1, 3) (1, 4) (1, 5) (1, 6) (3, 1) (3, 2) (3, 3) (3, 4) (3, 5) (3, 6) (5, 1) (5, 2) (5, 3) (5, 4) (5, 5)(5, 6)} 

C = Getting at most 5 as the sum of numbers on the two dices. 

C = {(1, 1)(1, 2)(1, 3)(1, 4)(2, 1)(2, 2)(2, 3)(3, 1)(3, 2)(4, 1)} 

D = Getting a sum greater than 5 but less than 10 

D = {(1, 5)(1, 6) (2, 4)(2, 5) (2, 6)(3, 3)(3, 4)(3, 5)(3, 6)(4, 2)(4, 3)(4, 4)(4, 5)(5, 1) (5, 2)(5, 3) (5, 4)(6, 1) (6, 2) (6, 3)} 

E = Getting at least 10 as the sum of numbers on the dices 

{(4, 6)(5, 5)(5, 6)(6, 4)(6, 5)(6, 6)} 

F = Getting an odd number on one of the dices 

{(1, 2)(1, 4)(1, 6)(2, 1)(2, 3)(2, 5)(3, 2)(3, 4)(3, 6)(4, 1)(4, 3)(4, 5)(5, 2)(5, 4)(5, 6)(6, 1)(6, 3)(6, 5) Now, 

(i) A and B = AՌB = Փ 

Since, There is no common events in Both A and B so the intersection is Null (Փ). 

⇒ B or C = BUC 

BUC = {(1, 1) (1, 2) (1, 3) (1, 4) (1, 5) (1, 6) (3, 1) (3, 2) (3, 3) (3, 4) (3, 5) (3, 6) (5, 1) (5, 2) (5, 3) (5, 4) (5, 5) (5, 6)(2, 1)(2, 2)(2, 3)(4, 1)} 

⇒ B and C = BՌC 

BՌC = {(1, 1), (1, 2)(1, 3)(1, 4)(3, 1)(3, 2)} 

⇒ A and E = AՌE 

AՌE = {(4, 6)(6, 4)(6, 5)(5, 6)(6, 6)} 

⇒ A or F = AUF 

AUF = {(2, 1)(2, 2)(2, 3)(2, 4)(2, 5)(2, 6)(4, 1)(4, 2)(4, 3)(4, 4)(6, 1)(6, 2)(6, 3)(6, 4)(6, 5)(6, 6)(1, 2)(1, 4)(1, 6) (3, 2)(3, 4)(3, 6)(4, 5)(5, 2)(5, 4)(5, 6)}

(ii) 

(a) True, because AՌB = Փ 

(b) True, because AՌB = Փ and AUB = S 

(c) False, because AՌC = Փ 

(d) False, because CՌD = Փ but CUD≠S 

(e) True, because CՌDՌE = Փ and CUDUE = S 

(f) True, because A’ՌB’ = Փ 

(g) False, because AՌBՌF = Փ and AUBUF = S

922.

Find the probability of getting R in the first place and M in the last place when all the letters of the word RANDOM are arranged in all possible ways.

Answer»

Here, there are 6 letters R, A, N, D, O, M in the word RANDOM.

∴ The total number of ways of arranging these six letters is,

n = 6P6 = 6! = 6 × 5 × 4 × 3 × 2 × 1 = 720.

A = Event that getting R in the first place and M in the last place.

∴ Favourable outcomes for the event A are obtained as follows:

∴ m = 1P1 × 4P4 × 1P1

= 1! × 4! × 1!

= 1 × 24 ×1 = 24

Hence p(A) = \(\frac{m}{n} = \frac{24}{720} = \frac{1}{30}\)

923.

One family is selected from the families having two children. The sex (male or female) of the children from this family is noted. State the sample space of this experiment and write the sets showing the following events:(1) Event A1 = One child is a female(2) Event A2 = At least one child is a female

Answer»

Here, let B = child is male;

G = child is female.

The sample space of selecting one family from the families having

two children is expressed as follows:
U = {(B, B), (B, G), (G, B), (G, G)}

(1) Event A1 = One child is a female

= {(B, G), (G, B)}

(2) Event A2 = At least one child is a female

= {(B, G), (G, B), (G, G)}

924.

A die is thrown 1000 times with the followingfrequencies for outcomes 1,2,3,4,5 and 6 as given below:Outcomes:    1              2              3                      4              5              6Frequency:    179          150          157                      149          175          190Find the probability of happening of each outcome.

Answer» Total number of outcomes=179+150+157+149+175+190=1000
`P(1)=179/1000`
`P(2)=150/1000`
`P(3)=157/1000`
`P(4)=149/1000`
`P(5)=175/1000`
`P(6)=190/1000`.
925.

Two coins are tossed simultaneous 500 times with the following frequencies of different outcomes. Two tails = 110 times One tail = 200 times No tail = 190 times Find the probability of occurrence of each events.

Answer» Let `E_(1)` = getting two tails = 110, `E_(2)` = getting one tail = 200, `E_(3)` = getting no tail = 190.
Total number of trials (n) = 500
`P(E_(1))=(E_(1))/(n)=(110)/(500)=(11)/(50)`
`P(E_(2))=(E_(2))/(n)=(200)/(500)=(2)/(5)`
`P(E_(3))=(E_(3))/(n)=(190)/(500)=(19)/(50)`
926.

A die is thrown 560 times. The number 6 appears on the upper face 72 times. A die is thrown at random. What is the probability of getting 6.

Answer» Total number of trials = 560
`"P (getting 6)"=("number of times 6 appears")/("total number of trials")=(72)/(560)=(9)/(70)`
927.

According to the mathematical definition of probability, what is the probability of each outcome among the n outcomes of a random experiment ?(a) 0(b) \(\frac{1}{n}\)(c) 1(d) cannot say

Answer»

Correct option is \((b) \frac{1}{n}\)

928.

Which random experiment from the following random experiments has an infinite sample space ?(a) Throwing two dice(b) Selecting two employees from an office(c) To measure the life of electric bulb(d) Select a card from 52 cards

Answer»

Correct option is (c) To measure the life of electric bulb

929.

Give two examples of random experiment.

Answer»

Two examples of random experiment are:

  1. The experiment of throwing a balanced die and
  2. The experiment of finding defective units from a lot of units produced.
930.

The following Venn diagram shows three events, A, B, and C, and also the probabilities of the various intersections. Determine (a) P(A) (b) `P(B nn barC)` (c ) `P(A uu B)` (d) `P(A nn barB)` (e) `P(B nn C)` (f) Probability of the event that exactly one of A, B, and C occurs.

Answer» From the above Venn diagram,
(a) `P(A) = 0.13 + 0.07 = 0.20`
(b) `P(B nn barC) = P(B) - P(B nn C)`
= 0.07 + 0.10 + 0.15 - 0.15 = 0.17
(c ) `P(A uu B) = P(A) + P(B) - P(A nn B)`
`= 0.13 + 0.07 + 0.07 + 0.10 + 0.15 - 0.07 = 0.45`
(d) `P(A nn barB) = P(A) - P(A nn B) = 0.13 + 0.07 - 0.07 = 0.13`
(e) `P(B nn C) = 0//15`
(f) P (exactly one of the three occurs) = 0.13 + 0.10 + 0.28 = 0.51
931.

Whenever horses `a , b , c`race together, their respective probabilities of winning the race are0.3, 0.5, and 0.2 respectively. If they race three times, the pr4obability that the same horse wins all the three races, and the probability that `a , b ,c`each wins one race are, respectively.`8//50 ,9//50`b. `16//100 ,3//100`c. `12//50 , 15//50`d. `10//50 ,8//50`A. `8//50,9//50`B. `16//100,3//100`C. `12//50,15//50`D. `10//50,8//50`

Answer» Correct Answer - A
`P(a)=0.3P(b)=0.5,P(c)=0.2.` Hence, a,b c are exhaustive. P(same horse wins all the three reces)
=P(aaa or bbb or ccc)
`=(0.3)^(3)+(0.5)^(3)+(0.2)^(3)`
`=(27=125+8)/(1000)=(160)/(1000)=4/25`
P(each horse wins exactly one race)
=P (abc or cab or bca or bac or cab or cba)
`=0.3xx0.5xx0.2xx6=0.18=9/50`
932.

A coin is tossed 1200 times whereby head occurred in 745 cases and in the reamaining tail occurred. Find the probability of each event.

Answer» Given that the coin is tossed 1200 times.
Total number of trials =1200
Let the event of getting a head be H, and getting a tail be T.
The numbre of times the event H occurred =745
Probability of event H, i.e., `P(H)=("Number of times head occurred")/("Total number of trials")=(745)/(1200)=(149)/(240)`
Number of times tail i.e., event T occurred =1200-745=455.
`:.` Probability of event T, i.e., `P(T)=("number of times head occurred")/("total number of trials")`
`=(455)/(1200)=(91)/(240)`
933.

A dice is rolled 100 times with the frequencies of the outcomes 1, 2, 3, 4, 5 and 6, which are given in the following table. Find the probaility of getting each outcome.

Answer» Given that the total number of trials = 100
Let each event be denoted by `E_(i)` where i =1, 2, 3, 4, 5 and 6.
Then probability of getting `1=P(E_(1))=("Frequency of 1")/("Total numbers of trials")=(10)/(100).`
Similarly, `P(E_(2))=(18)/(100),P(E_(3))=(15)/(100),P(E_(4))=(25)/(100),P(E_(5))=(20)/(100)and P(E_(6))=(12)/(100)`
934.

A coin is tossed 1000 times.Head occurred 625 times. Find the probability of getting a tail.A. `(5)/(8)`B. `(7)/(8)`C. `(1)/(8)`D. `(3)/(8)`

Answer» Correct Answer - D
P(getting a tail) `=("Numbre of times tail occured")/("Numbre of times coin tossed")`
935.

A coin is tossed 20 times and head occurred 12 times. How many times did tail occur?

Answer» Correct Answer - 8
936.

A coin is tossed 1000 times, if the probability of getting a tail is 3/8, how many times head is obtained?A. 525B. 375C. 625D. 725

Answer»

Possible outcomes of a coin = HT

So here,

There is an equal possibility of coming of Head and Tail in every toss.

Now it is given that probability of getting a tail = 38

The probability of getting a head = 1 - probability of getting a tail \(=1-\frac{3}{8}=\frac{5}{8}\)

The coin is tossed 1000 times.

Hence number of times a head obtained \(=\frac{5}{8}\times 1000=625\) times

937.

Two coins are tossed simultaneously. The probability of getting atmost one head isA. \(\frac{1}{4}\)B. \(\frac{3}{4}\)C. \(\frac{1}{2}\)D. \(\frac{1}{4}\)

Answer»

When two coins are tossed simultaneously then the possible outcomes obtained are {HH, HT, TH, and TT}.

Here H denotes head and T denotes tail.

Therefore, a total of 4 outcomes obtained on tossing two coins simultaneously.

The favourable outcome of getting at most one head are HT, TH, and TT.

So, the probability of getting at most one head is 3/4

938.

The game of “chuck-a-luck” is played at carnivals in some parts of Europe. Its rules are as follows: You pick a number from 1 to 6 and the operator rolls three dice. If the number you picked comes up an all the three dice, the operator pays you RS 3, if it comes up on two dice, you are paid Rs. 2; and if it comes on just one die, you are paid Rs 1. Only if the number you picked does not come up at all, you pay the operator Rs 1. The probability that you will win money playing in this game is : (a) 0.52 (b) 0.753 (c) 0.42 (d) None of these

Answer»

(c) 0.42

P(Particular number comes on the dice) = \(\frac{1}{6}\)

( there are in all 6 numbers)

P(particular number does not come on the dice) = 1 - \(\frac{1}{6}\) = \(\frac{5}{6}\)

As there are 3 dices, so,

P(Picked number does not come in any of dice) = \(\big(\frac{5}{6}\big)^3\)

P(You lose money) = \(\big(\frac{5}{6}\big)^3\) = \(\frac{125}{216}\) ≈ 0.58

∴ P(Winning) = 1 - 0.58 = 0.42

939.

What is the probability that a non-leap year has 53 Sundays?A  \(\frac{6}7\)B  \(\frac{1}7\)C  \(\frac{5}7\)D  None of these

Answer»

Total numbers of elementary events are: 7 

Let E be the event of having 53 Sundays 

Note- a non-leap year has 365 days or 52 weeks and 1 day. This one day could be any day amongst Sunday, Monday, Tuesday, Wednesday, Thursday, Friday or Saturday. Out of these favorable event is one; Sunday. 

Number of favorable outcome is = 1 

P (Sunday) = P (E) = \(\frac{1}7\)

940.

Which of the following cannot be the probability of occurrence of an event? A. 0.2 B. 0.4 C. 0.8 D. 1.6

Answer»

Probability of the occurrence of an event cannot be greater than 1. 

1.6 Which is greater than 1 is the correct answer

941.

The probability of an impossible event is A. 0 B. 1 C. \(\frac{1}2\)D. non-existent

Answer»

Probability of an impossible event is always zero (0)

942.

While tossing a coin the probability of getting head on upper side is A) 1/4 B) 1/2 C) 1/3 D) 3/4

Answer»

Correct option is: B) 1/2

943.

The probability of a certain event is A. 0 B. 1 C. \(\frac{1}2\)D. no existent 

Answer»

Probability of a certain event is always 1.

944.

Which of the following is an example for impossible event? i) Getting 7 on the top when a dice is rolled ii) Getting head on the top while tossing a coin iii) Picking a spade from a deck of playing cards iv) Picking an even prime number less than 2 A) Both (i) & (ii) B) Both (i) & (iii) C) Both (i) & (iv) D) Both (ii) & (iii)

Answer»

C) Both (i) & (iv)

945.

Which of the following is not to be a probability of any event ? A) 0 B) 1 C) – 0.2 D) 0.75

Answer»

Correct option is (C) –0.2

\(\because\) For any event, \(0\leq P(A)\leq1\)

Hence, probability of any event never be negative.

Therefore, - 0.2 never be the probability of any event.

Correct option is  C) – 0.2

946.

A bag contains 3 red balls, 5 black balls and 4 white balls. A balls is drawn at random from the bag. What is the probability that the ball drawn is: (i) white? (ii) red? (iii) black? (iv) not red?

Answer»

Total number of possible outcomes, n(S) = 12 {3 red balls, 5 black balls and 4 white balls) 

(i) n(E) = 4

∴ P(E) = \(\frac{n(E)}{n(S)}\) = \(\frac{4}{12}\) = \(\frac{1}{3}\)

(ii) n(E) = 3

∴ P(E) = \(\frac{n(E)}{n(S)}\) = \(\frac{3}{12}\) = \(\frac{1}{4}\)

(iii) n(E) = 5

∴ P(E) = \(\frac{n(E)}{n(S)}\) = \(\frac{5}{12}\)

(iv) n(E) = 9

 ∴ P(E) = \(\frac{n(E)}{n(S)}\) = \(\frac{9}{12}\) = \(\frac{3}{4}\)

947.

An urn contains 9 red, 7 white, and 4 black balls. A ball is drawn at random. Find the probability that the ball is drawn is red

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 20 balls is 20c1 = 20 

Our desired output is to pick a red ball. So, no. of ways to pick a red ball from 9 red balls (because the red ball can be picked from only red balls) is 9c1 = 9

Therefore, the probability of picking a red ball = \(\frac{9}{20}\)

Conclusion: Probability of picking a red ball from 9 red, 

7 white and 4 black balls is  \(\frac{9}{20}\)

948.

Class 9 Maths MCQ Questions of Probability with Answers?

Answer»

Class 9 Maths MCQ Questions of Probability with Answer are given here. Every one of the questions is arranged depending on the most recent exam pattern. Students can practice the part-savvy questions at Sarthaks eConnect and plan for the last, most important tests to score great marks. 

 Practicing Class 9 Maths important questions will help students to score good marks. After solving these MCQ Questions they get more confidence in the exams. 

Practice MCQ Questions for Class 9 Maths

1. When a die is thrown, the probability of getting an odd number less than 3 is 

(a) 1/6 
(b) 1/3 
(c) 1/2 
(d) 0

2. The probability of an event of a trial is always

(a) more than 1
(b) between 0 and 1 (both inclusive)
(c) 1
(d) 0

3. If two coins are tossed simultaneously, then what is the probability of getting exactly two tails?

(a) 1/4
(b) 1/2
(c) 1/3
(d) None of the above

4. Empirical probability is also known as 

(a) Classic probability
(b) Subjective probability
(c) Experimental probability
(d) None of the above

5. There are 4 green and 2 red balls in a basket. What is the probability of getting the red balls? 

(a) 1/2
(b) 1/3
(c) 1/5
(d) 1/6

6. Which of the following cannot be the probability of an event?

(a) 1
(b) 0
(c) 0.75
(d) 1.3

7. What is the probability of drawing a queen from the deck of 52 cards?

(a) 1/26
(b) 1/52
(c) 1/13
(d) 3/52

8. What is the probability that a leap year has 53 Sundays?

(a) 78
(b) 45
(c) 23
(d) 27

9. A card is selected from a deck of 52 cards. The probability of its being a red face card is 

(a) 3/26 
(b) 3/13 
(C) 2/13 
(D) 1/2

10.  An unbiased dice is thrown. What is the probability of getting an even number or a multiple of 3?
(a) 3/2
(b) 2/3
(c) 5/4
(d) 4/3

11. The sum of all probabilities equal to:

(a) 4
(b) 1
(c) 3
(d) 2

12. The probability of an impossible event is

(a) more than 1
(b) less than 1
(c) 1
(d) 0

13. Find the probability of a selected number is a multiple of 4 from the numbers 1, 2, 3, 4, 5, …15.

(a) 1/5
(b) 1/3
(c) 4/12
(d) 2/15

14. A card is drawn from a well-shuffled deck of 52 cards. What is the probability of getting a king of the red suits?

(a) 3/36
(b) 1/26
(c) 3/26
(d) 1/16

15. Performing an event once is called

(a) Sample
(b) Trial
(c) Error
(d) None of the above

16. What is the probability of getting an odd number less than 4, if a die is thrown?

(a) 1/6
(b) 1/2
(c) 1/3
(d) 0

17. Three coins were tossed 200 times. The number of times 2 heads came up is 72. Then the probability of 2 heads coming up is:

(a) 1/25
(b) 2/25
(c) 7/25
(d) 9/25

18. A batsman hits boundaries for 6 times out of 30 balls. Find the probability that he did not hit the boundaries.

(a) 1/5
(b) 2/5
(c) 3/5
(d) 4/5

19. If the probability of an event to happen is 0.3 and the probability of the event not happening is:

(a) 0.7
(b) 0.6
(c) 0.5
(d) None of the above

20. If P(E) = 0.38, then probability of event E, not occurring is:

(a) 0.62
(b) 0.38
(c) 0.48
(d) 1

Answer: 

1. Answer: (a) 1/6 

Explanation: When a die is thrown, then total number of outcomes = 6

Odd number less than 3 is 1 only.

Number of possible outcomes = 1

∴ Required probability = 1/6

2. Answer: (b) between 0 and 1 (both inclusive)

3. Answer: (a) 1/4

Explanation: If two coins are tossed, then the sample space, S = {HH, HT, TH, TT}

Favourable outcome (Getting exactly two tails) = {TT} 

Therefore, the probability of getting exactly two heads = 1/4

4. Answer: (c) Experimental probability

Explanation: Empirical probability is also known as experimental probability.

5. Answer: (b) 1/3

Explanation: Total balls = 4 green + 2 red = 6 balls

No. of red balls = 2.

Hence, the probability of getting the red balls = 2/6 = 1/3

6. Answer: (d) 1.3

Explanation: The probability of an event always lies between 0 and 1.

7. Answer: (c) 1/13

Explanation: Total cards = 52

Number of queens in a pack of 52 cards = 4

Hence, the probability of drawing a queen from a deck of 52 cards = 4/52 = 1/13.

8. Answer: (d) 27

Explanation: The two odd days can be {Sunday,Monday},{Monday,Tuesday},{Tuesday,Wednesday}, Wednesday,Thursday},{Thursday,Friday},{Friday,Saturday},{Saturday,Sunday}.
So there are 7 possibilities out of which 2 have a Sunday. So the probability of 53 Sundays in a leap year is 2/7.

9. Answer: (a) 3/26 

Explanation: In a deck of 52 cards, there are 12 face cards i.e. 6 red (3 hearts and 3 diamonds) and 6 black cards (3 spade and 3 clubs) 

So, probability of getting a red face card = 6/52 = 3/26

10. Answer: (b) 2/3

Explanation: In a single throw of dice, we get 1,2,3,4,5 or 6.

No. of total outcomes =6

Even number or a multiple of 3 are 2,3,4,6

Favourable no. of outcomes = 4

P(even number or multiples of 3)= 4/6=2/3

11. Answer: (b) 1

12.  Answer: (d) 0

13. Answer: (a) 1/5

Explanation: S = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}

Multiples of 4 from the sample space = {4, 8, 12}

Therefore, the probability of the selected number is a multiple of 5 is 3/15 = 1/5.

14. Answer: (b) 1/26

Explanation: In a pack of 52 cards, there are a total of 4 king cards, out of which 2 are red and 2 are black.

Therefore, in a red suit, there are 2 king cards. 

Hence, the probability of getting a king of red suits = 2/52 = 1/26.

15. Answer: (b) Trial

Explanation: Performing an event once is called a trial.

16. Answer: (c) 1/3

Explanation: Sample space, S = {1, 2, 3, 4, 5, 6}

Favourable outcomes = {1, 3}

Therefore, the probability of getting an odd number less than 4 = 2/6 = 1/3.

17. Answer: (d) 9/25

Explanation: Probability = 72/200 = 9/25

18. Answer: (d) 4/5

Explanation: No. of boundaries = 6

No. of balls = 30

No. of balls without boundaries = 30 – 6 =24

Probability of no boundary = 24/30 = 4/5

19. Answer: (a) 0.7

Explanation: Probability of an event not happening = 1 – P(E)

P(not E) = 1 – 0.3 = 0.7

20. Answer: (a) 0.62

Explanation: P(not E) = 1 – P(E) = 1-0.38 = 0.62

Click here to practice Probability MCQ Questions for Class 9 Maths

949.

Which of the following cannot be the probability of occurrence of an event?(i)  0(ii)   \(-\frac{3}{4}\)  (iii)  \(\frac{3}{4}\) (iv)  \(\frac{4}{3}\)

Answer»

(ii) and (iv) can’t be the probability of occurrence of an event. So, (ii) and (iv) are the answers to our question. 

Explanation: We know that,

0 ≤ probability ≤ 1 i.e. probability can vary from 0 to 1(both are inclusive) So, (i) 0 can be possible as 0 ≤ probability ≤ 1

(ii)    \(-\frac{3}{4}\)  is not possible as it is less than 0 

(iii)    \(\frac{3}{4}\)  is possible as 0 ≤ probability  ≤ 1

(iv) \(\frac{4}{3}\) is not possible as it is greater than 1 

Conclusion:   \(\frac{3}{4}\)  and   \(-\frac{3}{4}\) are the probabilities that cannot occur.

950.

If a letter is chosen at random from the English alphabet, find the probability that the letter is chosen is (i) a vowel (ii) a consonant

Answer»

(i) We know that,

Probability of occurrence of an event

   = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) 

Total possible outcomes are alphabets from a to z 

Desired outcomes are a, e, i, o, u 

Total no. of outcomes are 26 and desired outputs are 5 

Therefore, the probability of picking a vowel = \(\frac{5}{26}\)

Conclusion: Probability of choosing a vowel is  \(\frac{5}{26}\)

(ii) We know that, 

Probability of occurrence of an event 

   = \(\frac{Total\,no.of\,Desired\,outcomes}{Total\,no.of\,outcomes}\) 

Total possible outcomes are all alphabets from a to z

Desired outcomes are all alphabets except a, e, i, o, u 

Total no. of outcomes are 26 and desired outputs are 21 

Therefore, the probability of picking a consonant = \(\frac{21}{26}\)

Conclusion: Probability of choosing a consonant is  \(\frac{21}{26}\)