CampusFest is a student festival where local businesses come on campus to sell their goods to students at vastly reduced prices. As part of a give-away promotion, a local cellular phone company gave away 500 cellular phones to students who signed up for their calling service. Unbeknownst to the company is that 60 of these cellular phones were faulty and will cause a small explosion when dialed outside the local calling area. Suppose you and your roommate each received one of the giveaway phones. Find the probability that both of you received faulty phones. Round to five decimal places when necessary.
A) 0.10581
B) 0.0144
C) 0.24
D) 0.01419

Question

Quizplus · Accepted Answer

The probability that both phones are faulty is found by multiplying the probability of one phone being faulty by the probability of the second phone being faulty given the first is faulty. The probability of the first phone being faulty is 60/500. After one faulty phone is taken, there are 59 faulty phones left out of 499 phones total. So, the probability for the second phone is 59/499. Multiplying these probabilities gives (60/500) * (59/499) = 0.01419.

CampusFest Is a Student Festival Where Local Businesses Come on Campus