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 am, at what time will he first touch a flag at 120 feet from the ground?
Explanation
1. Net Climb per cycle:
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Distance climbed = 30 feet
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Distance slipped = 20 feet
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Net climb in 1 hour = 30−20=10 feet/hour
2. Identifying the Final Jump:
The monkey will touch the flag during his upward climb before he slips back.
3. Time taken to reach 90 feet:
Time=10 feet/hour90 feet=9 hours
4. The Final Hour:
After 9 hours, the monkey is at 90 feet.
In the 10th hour, he climbs 30 feet:
Total Height=90+30=120 feet
He touches the flag at the end of his climb in the 10th hour.
5. Total Time Calculation:
Correct Answer: Option C