Escape the Well!
Algebra
Level
3
A monkey sadly falls down a well 25m deep. Being agile however, it can slowly climb back up. Every 3 hours it climbs up 4m, but then at the end of this period, it slips back 1m.
Assuming that it does not sleep or rest, how many hours does it take to get out of the well?
25
8
24
21
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1 solution
After every cycle, the monkey climbs 3 metres up the well. However at 21m, after the 4m, it gets out before it can slip, hence the monkey takes 7 × 3 + 3 hours = 24.