Question employ

3.5 Probability & Conditional Probability - Conditional probability formula
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Employees working for a customer service line at an electric company recorded all the calls last Monday and noted whether the caller asked for repairs and whether the caller asked about a bill. The results are summarized in the table below.

Asked for
 repairs
Did not ask
 for repairs
Total
Asked
 about a bill
48 623 671
Did not ask
 about a bill
130 90 220
Total 178 713 891

If a caller last Monday who asked about his or her bill is selected at random, which of the following is closest to the probability that the customer also asked for repairs?

A.

0.05

B.

0.07

C.

0.20

D.

0.27

Employees working for a customer service line at an electric company recorded all the calls last

Hard-difficulty · SAT Math · Probability & Conditional Probability — Conditional probability formula. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.

Answer explanation

Choice B is correct. According to the table, a total of 671 customers asked about a bill. Of these, 48 also asked for repairs. Therefore, if a customer who asked about a bill is selected at random, the probability that the customer also asked for repairs is 48 over 671 is approximately equal to 0 point 0 7.

Choice A is incorrect. This is the probability that a customer selected at random from all customers who called on Monday both asked for repairs and asked about a bill. Choice C is incorrect. This is the probability that a customer selected at random from all customers who called on Monday asked for repairs, regardless of whether or not the customer asked about a bill. Choice D is incorrect. This is the probability that a customer selected at random from those who asked for repairs also asked about a bill.