InterviewSolution
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Cards bearing numbers 1,3,5,......,35 are kept in a bag. A card is drawn at random from the bag. Find the probability of getting a card bearing(i) A prime number less than 15,(ii) A number divisible by 3 and 5. |
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Answer» Given numbers 1,3,5.....35 form an AP with a = 1 and d = 2 Let Tn = 35 Then, 1 + (n - 1)2 = 35 ⇒ 1 + 2n - 2 = 35 ⇒ 2n = 36 ⇒ n = 18 Thus, Total number of favorable outcomes = 18 (i) Let E1 be the event of getting a prime number less than 15. out of these numbers, prime numbers less than 15 are 3,5,7,11 and 13. The number of favorable outcomes = 5 Therefore P(getting a prime number less than 15) = P(E1) = \(\frac{number\,of\,outcomes\,favorable\,to\,E_1}{number\,of\,all\,possible\,outcomes}\) = \(\frac{5}{18}\) Thus, the probability of getting card bearing a prime number less than 5 is \(\frac{5}{18}\) (ii) Let E2 be the event of getting a number divisible by 3 and 5 out of these numbers, the number divisible by 3 and 5 means number divisible by 15 is 15 The number of favorable outcomes = 1 Therefore P(getting a number divisible by 3 and 5) = P(E2) = \(\frac{number\,of\,outcomes\,favorable\,to\,E_2}{number\,of\,all\,possible\,outcomes}\)= \(\frac{1}{18}\) Thus, the probability of getting card bearing a number divisible by 3 and 5 is \(\frac{1}{18}\) |
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