A night watchman is required to check in every 40 minutes while making his rounds, to list tour of duty extends from 9:00 P.M. to 5:00 A.M.
If he checks in at the start of his rounds and also when lie finishes, how many times does he check in during the night?
Answer(s): B
Explanation:
From 9:00 P.M. to 5:00 A.M. is a tour of duty of 8 hours. Since 60 minutes = 1 hour, when the watchman checks in every 40 minutes he checks in every 40/60, or every 2/3, of an hour.
8/1 ÷ 2/3 = 8/1 × 3/2 = 12
The watchman must check in once at the beginning of each of the twelve 40-minute periods, or 12 times. But he must also check in at the end of the last period. Thus, he checks in 12 + 1, or 13, times.