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Official Guide Quant Review #110

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Official Guide Quant Review #110

by drhomler » Wed May 30, 2007 6:12 pm
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 begininng 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

Can someone please break down the wording on this one. Explain it to me as if I were three years old and just learned to read. I dont understand what is saying. The explanation in the back is light on usefulness as well. The math is simple division and multiplication but I dont know what is being asked. And yes I am a native english speaker. Thank you so much in advance for your time, whoever you maybe.
OA-D
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Re: Official Guide Quant Review #110

by jayhawk2001 » Wed May 30, 2007 8:52 pm
drhomler wrote: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 begininng 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
Let S denote the stroke and I denote the "interval" between 2 succesive
strokes.

At 6:00, the pattern will look like below

SISISISISIS

As you can see, there are a total of 6 strokes and 5 intervals for a
total of 11 "events" if you may. The duration for these 11 events = 22
sec which implies each S or I takes 2 sec.

For 12:00, the pattern will be SISISISISISISISISISISIS for a total
of 23 events. 23 * 2 = 46 seconds.
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by drhomler » Thu May 31, 2007 5:48 am
Thanks Jay, I really appreciate it. For someone reason when I read that, I cant discern what is stated about the interval in relation to the clock striking. But your explanation is very helpful. Hope I dont see on eof those on the real thing unless it is identical to that. That was 110 out of 180 so I guess that makes it a 600 level question, for me its an 800 juist goes to show what they think is easy relative to what you think is easy are two very different things.
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by 800GMAT » Fri Jun 01, 2007 1:25 pm
the number of intervals between the beginning and end of each hourly stroke will be one less than the hourly time

So 6:00 will have 5 intervals, 7 will have 6 intervals, so on and so forth
let x = the time required for a stroke
this is equal to the time interval between strokes.

at 6, the clock will strike 6 times and the intervals will be 5
6x+5x=11x=22
x=2

at 12 , the clock will strike 12 times and the intervals will be 11
so 12x+11x= 23x= 23*2=46
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