Question

A box contains 19 balls bearing numbers 1, 2, 3, ..., 19. A ball is drawn at random from the box. What is the probability that the number of the ball is a prime number?

Answer 1

Given: A box contains balls numbered 1 through 19; one ball is drawn at random. Find the probability the number is prime.

Step-wise calculation:

1. List the prime numbers ≤ 19: 2, 3, 5, 7, 11, 13, 17, 19.

2. Number of favourable outcomes = 8.

3. Total number of equally likely outcomes = 19.

4. Probability = `"Favourable outcomes"/"Total outcomes"`

= `8/19`

The probability that the drawn number is prime is `8/19`.