InterviewSolution
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Card numbered 1 to 30 are put in a bag. A card is drawn at random from the bag . Find the probability that the number on the drawn card is(i) Not divisible by 3,(ii) A prime number greater than 7,(iii) Not a perfect square number. |
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Answer» The total number of outcomes = 30. (i) Let E1 be the event of getting a number not divisible by 3. out of these numbers, numbers divisible by 3 are 3,6,9,12,15,18,21,245,27 and 30. number of favorable outcomes = 30 - 10 = 20 Therefore P(getting a number not divisible by 3) = P(E1) = \(\frac{number\,of\,outcomes\,favorable\,to\,E_1}{number\,of\,all\,possible\,outcomes}\) = \(\frac{20}{30}\) = \(\frac{2}{3}\). Thus, the probability that the number on the card is not divisible by 3 is \(\frac{2}{3}\). (ii) Let E1 be the event of getting a prime number greater than 7. out of these numbers, prime numbers greater than 7 are 11,13,17,19,23 and 29. number of favorable outcomes = 6 Therefore P(getting a prime number greater than 7) = P(E2) = \(\frac{number\,of\,outcomes\,favorable\,to\,E_2}{number\,of\,all\,possible\,outcomes}\) = \(\frac{6}{30}\) = \(\frac{1}{5}\). Thus, the probability that the number on the card is a prime number greater than 7 is \(\frac{1}{5}\). (iii) Let E3 be the event of getting a number which is not a perfect square number. out of these numbers, perfect square numbers are 1,4,9,16 and 25. number of favorable outcomes = 30 - 5 = 25 Therefore P(getting non-perfect square number) = P(E3) = \(\frac{number\,of\,outcomes\,favorable\,to\,E_3}{number\,of\,all\,possible\,outcomes}\) = \(\frac{25}{30}\) = \(\frac{5}{6}\). Thus, the probability that the number on the card is not a perfect square number is \(\frac{5}{6}\). |
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