Question

A box contains 24 cards numbered $1,2,3,4, \ldots, 24$ which are mixed thoroughly. A card is drawn at random from the box.
Find the probability that the number on the card is prime.

• A. $\frac{1}{4}$
• B. $\frac{5}{8}$
• C. $\frac{3}{8}$
• D. None

Answer 1

Answer: (C)

Let $E$ be an event that the number on the card is prime.
Then $E=\{2,3,5,7,11,13,17,19,23\}$
$n(E)=9$
Total possible outcomes $n(S)=24$
Required probability $=\frac{n(E)}{n(S)}=\frac{9}{24}=\frac{3}{8}$