2008 AMC 10A Problem 1

Question

A bakery owner turns on his doughnut machine at

8{:}30

am. At

11{:}10

am the machine has completed one third of the day’s job. At what time will the doughnut machine complete the job?

1{:}50

pm

3{:}00

pm

3{:}30

pm

4{:}30

pm

5{:}50

pm

Find how long one third of the job takes, in minutes

The whole job takes three times as long, measured from the

8{:}30

am start

From

8{:}30

am to

11{:}10

am is

2

hours and

40

minutes, or

160

minutes, to finish one third of the job.

The entire job therefore takes

3 \cdot 160 = 480

minutes, or

8

hours.

Eight hours after

8{:}30

am is

4{:}30

pm.

Thus, the correct answer is D.

Problem 1 in other years