Question

A box contains cards numbered 3,5,7,9,…,35,37. A card is drawn at random from the box. Find the probability that the number on the card is a prime number.

Answer 1

Correct Answer - ` 11/18`
Given numbers 3,5,7,9,…,35,37 from an AP with a = 3 and d = 2.
Let ` T_(n) = 37`. Then,
` 3 +(n-1) xx 2 = 27 rArr (n-1) xx 2 = 34 rArr n - 1 = 17 rArr n = 18`.
Out of these numbers, the prime numbers are 3,5,7,11,13,17,19,23,29,31,37.
Their number is 11.
` :. ` P(getting a prime number ) = ` 11/18`.