Two machines that fill cereal boxes work at the same rate. After they work for 5 h, one machine breaks down. The second machine requires 10 more hours to finish filling the boxes. How long would it have taken one of the machines, working alone, to fill the boxes?
A) 23 h
B) 21 h
C) 10 h
D) 24 h
E) 20 h

Question

Quizplus · Accepted Answer

When both machines work together for 5 hours, they complete half of the job (since the second machine needs 10 more hours to finish the job alone, which is the same amount of time both machines worked together). Therefore, one machine working alone would take 2 * 10 = 20 hours to complete the job.

Two Machines That Fill Cereal Boxes Work at the Same