A monkey climbs 30 feet 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?

The monkey climbs 30 feet and slips back 20 feet each hour, gaining 10 feet net per hour. After 7 hours (from 8 a.m. to 3 p.m.), he reaches 70 feet. At the beginning of the 8th hour (starts at 3 p.m.), he climbs 30 feet from 70 to 100 feet. At the beginning of the 9th hour (starts at 4 p.m.), he climbs from 100 to 130 feet, touching the 120-foot flag at 6 p.m. (after 10 hours from 8 a.m., which is 6 p.m.).