Find the probability that a prime number is chosen.

Question

You have an equally likely chance of choosing any integer from 1 through 20. Find the probability that a prime number is chosen.

1. 2/5
2. 9/20
3. 11/20
4. 1/2

Answer 1

There are 8 prime numbers between 1 and 20: 2, 3, 5, 7, 11, 13, 17, and 19 (Note: 1 is not prime)

Probability of choosing a prime = 8/20 = 2/5