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another OG question..#110

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by jamesk486 » Tue Apr 10, 2007 4:31 am
A certain clock marks every hour by striking a # of times equal to the hour, and the time required for a stroke is exactly equal to the time interval between the 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

The answer explanation is so obscure that I don't know what they're talking about! :oops:
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Re: another OG question..#110

by gabriel » Tue Apr 10, 2007 5:13 am
jamesk486 wrote:A certain clock marks every hour by striking a # of times equal to the hour, and the time required for a stroke is exactly equal to the time interval between the 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

The answer explanation is so obscure that I don't know what they're talking about! :oops:
let the time for a stroke be x ... let the timer between the stroke be y .. now at 6 .. the clock will strike 6 times and the no of intervals between the strokes is 5 . so the total time will be x+y+x+y+x+y+x+y+x+y+x = 6*x + 5*y .. but x = y .. so the total time is 11*x =22 .. so x = 2..

therefore, the time for a stroke = the interval between the stroke = 2 seconds ...

at 12 .. the no of times the clock will strike is 12 and the no of intervals between the stroke is 11 .. therfore the total = (12+11)*x= 23*2 = 46 seconds .. now the q asks for the time elapsecd after the first stroke and the last stroke .. the first stroke will take 2 seconds .. so the time elapsed = total - 2 = 46-2 =44 seconds.. so the answer is E ... hope it helps..
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by Cybermusings » Tue Apr 10, 2007 11:10 am
Thanks Gabriel...Pretty obscure question!
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by jamesk486 » Wed Apr 11, 2007 1:11 am
yes, thank you! i definitely understand now~
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by tallazndood » Mon Dec 21, 2009 7:28 pm
gabriel wrote: let the time for a stroke be x ... let the timer between the stroke be y .. now at 6 .. the clock will strike 6 times and the no of intervals between the strokes is 5 . so the total time will be x+y+x+y+x+y+x+y+x+y+x = 6*x + 5*y .. but x = y .. so the total time is 11*x =22 .. so x = 2..

therefore, the time for a stroke = the interval between the stroke = 2 seconds ...

at 12 .. the no of times the clock will strike is 12 and the no of intervals between the stroke is 11 .. therfore the total = (12+11)*x= 23*2 = 46 seconds .. now the q asks for the time elapsecd after the first stroke and the last stroke .. the first stroke will take 2 seconds .. so the time elapsed = total - 2 = 46-2 =44 seconds.. so the answer is E ... hope it helps..
Thank you for the explanation, Gabriel! It really helped me understand where did "11" come from. For the record, the official answer is D: 46 seconds. I think subtracting 2 seconds for the first stroke is unnecessary since the q did ask "between the beginning of the first stroke and...".
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by Shahadot » Sat Feb 04, 2012 11:18 pm
At 6>>>>strike-pause,strike-pause,strike-pause,strike-pause,strike-pause,strike
so 11x=22
therefor x=2
At 12>>>> 23x
therefor, 23*2=46
so Answer is D
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by Anurag@Gurome » Sun Feb 05, 2012 5:59 pm
jamesk486 wrote:A certain clock marks every hour by striking a # of times equal to the hour, and the time required for a stroke is exactly equal to the time interval between the 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

The answer explanation is so obscure that I don't know what they're talking about! :oops:
At 6, there are 6 strokes and 5 intervals between strokes.
Let t = time required for a stroke = time interval between strokes.
Thus, the 6t + 5t = 22 implies t = 2

At 12, 12 strokes and 11 intervals implies 12t + 11t = 23t = 23 * 2 = 46

The correct answer is D.
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