Dave can answer each problem on a certain test in 6 minutes. Michael
can answer each problem in 1 minute. Suppose Michael rests for two
hours in the middle of answering the problems but Dave works straight
through the test without stopping. Suppose further that they nish
the test at the same time. How long did it take Dave to answer all the
problems?  Choose one:
A) 2 hours and 10 minutes
B) 2 hours and 12 minutes
C) 2 hours and 15 minutes
D) 2 hours and 18 minutes
E) 2 hours and 24 minutes
Let n be the number of problems on the test. Then Dave took 6n minutes   to complete the test and Michael took 2 hours and n minutes (i.e., 120 + n minutes) to   complete the test. Therefore, 6n = 120 + n which implies that n = 24. Since the amount   of time to complete the test was the same for Dave and Michael, it took Dave 2 hours and   24 minutes to answer all the problems   correct answer 2 hours and 24 minutes
<result>E</result>
Dave can answer each problem on a certain test in 6 minutes. Michael
can answer each problem in 1 minute. Suppose Michael rests for two
hours in the middle of answering the problems but Dave works straight
through the test without stopping. Suppose further that they nish
the test at the same time. How long did it take Dave to answer all the
problems?