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Quantitative Review 2nd Edition- Problem 110

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by cardoc » Wed Oct 26, 2011 4:46 am
A certain clock marks every hour by striking a number of times equal to the hour and the time required for a stroke is exactly equal to the time interval between strokes. At 6.00 the time lapse between the beginning of the first stroke and the end of the last stroke is 22 seconds. At 12:00, how many seconds elapse between the beginning of the first stroke and the end of the last stroke.

A) 72
B) 50
c) 48
D) 46
E) 44

Answer - D. Please could someone provide an explanation for this problem
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Source: — Problem Solving |

by neelgandham » Wed Oct 26, 2011 5:29 am
Let | be the stroke and _ be the interval between strokes.

At 6:00 |_|_|_|_|_| - 6 strokes and 5 intervals = 22seconds. The time required for a stroke is exactly equal to the time interval between strokes

=> 1 stroke = 1 interval,
So, 6 strokes + 5 intervals = 22seconds
=> 6 strokes + 5 strokes = 22seconds
=> 11 Strokes = 22 seconds
So it takes 2 seconds for a stroke, followed by a 2 second interval. -(1)

At 12 |_|_|_|_|_|_|_|_|_|_|_| - 12 strokes and 11 intervals = Time taken by 23 strokes = 23*2 secs (from 1) = 46 secs
Anil Gandham
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by cardoc » Wed Oct 26, 2011 7:08 am
Thanks , Appreciate the quick response.
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