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A monkey climbing up a greased pole ascends 12 metres and slips down 5 metres in alternate minutes. If the pole is 63 metres high, how long will it take him to reach the top?
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- 18 minutes
- 16 minutes
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16 7 minutes 12 - 18 minutes 20 seconds
Correct Option: C
In 1 minute the monkey climbs 12 metres but then he takes 1 minute to slip down 5
metres. So, at the end of 2 minutes the net ascending of the monkey is 12 – 5 = 7 metres.
So, to cover 63 metres the above
| process is repeated | = 9 | |
| 7 |
times. Obviously, in 9 such happenings the monkey will slip 8 times, because on 9th time, it
will climb to the top. Thus, in climbing 8 times and slipping 8 times, he covers 8 × 7 = 56 metres.
Time taken to cover 56 metres
| = | = 16 minutes | |
| 7 |
Remaining distance
= 63 – 56 = 7 metres
Time taken to ascend 7 metres
| = | minutes | |
| 12 |
| ∴ Total time taken = 16 + | |
| 12 |
| = 16 | minutes. | |
| 12 |
