Multiple-Choice Questions: GRE Preparation

[engmahbub091]

Question:

In a certain medical group, Dr. Schwartz schedules appointments to begin 30 minutes apart, Dr. Ramirez schedules appointments to begin 25 minutes apart, and Dr. Wu schedules appointments to begin 50 minutes apart. All three doctors schedule their first appointments to begin at 8:00 in the morning, which are followed by their successive appointments throughout the day without breaks. Other than at 8:00 in the morning, at what times before 1:30 in the afternoon do all three doctors schedule their appointments to begin at the same time?

Indicate all such times.

A. 9:30 in the morning
B. 10:00 in the morning
C. 10:30 in the morning
D. 11:00 in the morning
E. 11:30 in the morning
F. 12:00 noon
G. 12:30 in the afternoon
H. 1:00 in the afternoon

Can anyone explain the answer of this question for me?

thanks in advance

[tommywallach]

Hey Engma,

Honestly, the easiest way to do this question is to write them all out, because the time range of 8:00am to 1:30pm is pretty small.

You could work out a system, however, if you needed to figure this out for a much larger time range. Perhaps like so:

25: 25, 50, 75, 100, 125, 150
30: 30, 60, 90, 120, 150
50: 50, 100, 150

As we can see here, the doctors all line up every 150 minutes from the starting point. That's every 2.5 hours. So they'll meet at 10:30am and 1:00pm.

-t