A monkey climbs 30 feet at the beginning of each hour and rests for a while when he slips back 20feet before he again starts climbing at the beginning of the next hour if he begins his ascent at 9 a?

The monkey climbs 30 feet at the beginning of each hour but slips back 20 feet afterward, resulting in a net gain of 10 feet per hour. Therefore, after the first hour, he reaches 10 feet, after the second hour he reaches 20 feet, and so on. When he reaches 30 feet at the beginning of the fourth hour, he will not slip back since he has already reached the top, completing his ascent at 11 a.m.