A monkey climbs 30 feet before at the beginning of each hour and rests for a while when he slips back 20 feet before he again starts climbing in the beginning of the next hour. If he begins his ascent at 8.00 a.m, at what time will he first touch a flag at 120 feet from the ground ?

A. 4 p.m.
B. 5 p.m.
C. 6 p.m.
D. None of these
Answer: C . 6 p.m.

Justification: Clearly, the monkey climbs 10 feet in one hour. SO, it will climb upto a height of 90 feet in 9 hours i.e. at 5.00 p.m. It will then ascend a height of 30 feet in the next hour too touch the peak at 6.00 p.m.