Problem Solving - 3

There are two buses A and B. On Monday, bus A departs at 3pm and bus B at 4pm. After this, bus A departs every 10 hours and bus B every 15 hours. What is the earliest day they will depart at the same time?

A). Tuesday

B). Wednesday

C). Thursday

D). Sunday

E). so long as they continue operating in this manner, they will never leave at the same time.

Answer - E is the right choice.

The LCM of 10 hours and 15 hours = 30 hours,
30 hours = 6 hours mod 24 hour (day)

After that period they will just repeat the cycle.