Question

10 cards are numbered from 1 to 10 and placed in a box. One card is selected at random and is not replaced. Another card is then randomly selected. What is the probability of selecting two prime numbers?

A. 2/15



B. 4/18



C. 7/90



D. 1/10

Answer 1

2/15.

Explanation:

The prime numbers in the first 10 numbers are: 2, 3, 5, 7 . That is a total of 4.

Prob( first number drawn is prime) = 4/10 = 2/5.

Prob( second number drawn is prime) = 3/9 = 1/3.

Required probability is 2/5 * 1/3

= 2/15.