As part of a promotion, both you and your roommate are given free cellular phones from a batch of 13 phones. Unknown to you, four of the phones are faulty and do not work. Find the probability that one of the two phones is faulty.
A) .462
B) .538
C) .231
D) .077

Question

Quizplus · Accepted Answer

The probability that one of the two phones is faulty can be calculated by considering the combinations of selecting one faulty and one non-faulty phone. There are 4 faulty phones and 9 non-faulty phones. The probability is calculated as (4/13) * (9/12) + (9/13) * (4/12) = 0.462.

As Part of a Promotion, Both You and Your Roommate