Bob ran a 20 mile race. At what time did he finish the race? : DS Archive
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# Bob ran a 20 mile race. At what time did he finish the race?

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Bob ran a 20 mile race. At what time did he finish the race? [#permalink]

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06 Mar 2006, 13:41
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Bob ran a 20 mile race. At what time did he finish the race?
1. He started the race at 8:05 am and his average speed for the first 10 miles of the race was 8 miles per hour.

2. He had completed half the amount of running time at 9:20 am and had completed the 80% of running time at 10:05 am.
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06 Mar 2006, 14:14
B. He finished 30% of running time between 9:20AM and 10:05AM.
Therefore, 100% is 2hours and 30minutes. He finished 50% by 9:20, so he must have started at 8:05AM. He arrived at the finish line at 10:35AM.
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06 Mar 2006, 18:50
We dont know at what pace or rate he was running the last 20%. There isn't sufficient information at all. I would go with E
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06 Mar 2006, 19:47
B.
30% of total time = 45 minuets
20% of total time = (45/3)(2) minuets = 30 minuets.

so the time he finished the race is 10:35.
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06 Mar 2006, 23:36
I agree with B since we dont need to know the time required to finish the last 20%. We already know the percent of time at 2 stages. That should suffice. OA please.
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07 Mar 2006, 07:54
All of you guys are wrong.. give it one more shot!
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07 Mar 2006, 08:11
bewakoof wrote:
All of you guys are wrong.. give it one more shot!

I am tempted to choose E but again according to Bewakoof this is a wrong answer. OA please!
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07 Mar 2006, 10:15
MBAHopeful wrote:
bewakoof wrote:
All of you guys are wrong.. give it one more shot!

I am tempted to choose E but again according to Bewakoof this is a wrong answer. OA please!

actually according to Kaplan it is wrong.. Kaplan says it is C..
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07 Mar 2006, 10:36
bewakoof wrote:
MBAHopeful wrote:
bewakoof wrote:
All of you guys are wrong.. give it one more shot!

I am tempted to choose E but again according to Bewakoof this is a wrong answer. OA please!

actually according to Kaplan it is wrong.. Kaplan says it is C..

Hello Bewakoof,

As I do not have Kaplan, can you please let us know the Kaplan explaination if there is any? I find it rather difficult to believe that the answer is C, but again may be I am ovelooking some minute details.
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07 Mar 2006, 10:57
anandsebastin wrote:
B. He finished 30% of running time between 9:20AM and 10:05AM.
Therefore, 100% is 2hours and 30minutes. He finished 50% by 9:20, so he must have started at 8:05AM. He arrived at the finish line at 10:35AM.

I agree. bwk, does Kaplan gives OE in this case?
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07 Mar 2006, 11:52
Look at the attachment.. If that does not work.. I will try to explain it in my own words.

btw.. I did get it wrong.. during my practice tests.. I got 5-6 weird questions like these.. my Math score was 40!
Attachments

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07 Mar 2006, 12:08
bewakoof wrote:
Look at the attachment.. If that does not work.. I will try to explain it in my own words.

btw.. I did get it wrong.. during my practice tests.. I got 5-6 weird questions like these.. my Math score was 40!

Hello again,

It seems I did not understand the explaination.
As I understand the explaination in the case 2) Kaplan has translated the total time required in the equation 3T/10 = 45. In this equation aren't they assuming that the person is running with a constant rate through out his race?

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07 Mar 2006, 12:21
I really dont know. I chose E just like you guys did..

I think the trick lies in understanding "running time".. 80% running time is covered in 9:20 and 50% is covered at a:bb. so we really dont care about the speed.. All we need is the time for our motives..
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07 Mar 2006, 12:32
bewakoof wrote:
I really dont know. I chose E just like you guys did..

I think the trick lies in understanding "running time".. 80% running time is covered in x:xx and 50% is covered at x:xx.. so we really dont care about the speed.. All we need is the time for our motives..

I guess you are right. If we consider both the cases together, we can see that from 80% of running 50% and 30% runnings are done with the same rate so I think the statistical assumption is the remaining 20% is done with the same rate.

Sorry for keep bugging you guys with my questions.
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07 Mar 2006, 13:15
bewakoof wrote:
Look at the attachment.. If that does not work.. I will try to explain it in my own words.

btw.. I did get it wrong.. during my practice tests.. I got 5-6 weird questions like these.. my Math score was 40!

As per explanation for S2,
"number of minutes he spent running" is known (02:30 hrs).
also we know, he had run for "01:15 hrs" at "09:20" (50% of running time). Why can't we calculate the time when he "begun" race (09:20 - 01:15 = 08:05 hrs).

Explanation says "we do not know when he began running.". I guess we do. Wats your take?
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07 Mar 2006, 13:31
MBAHopeful wrote:
bewakoof wrote:
I really dont know. I chose E just like you guys did..

I think the trick lies in understanding "running time".. 80% running time is covered in x:xx and 50% is covered at x:xx.. so we really dont care about the speed.. All we need is the time for our motives..

I guess you are right. If we consider both the cases together, we can see that from 80% of running 50% and 30% runnings are done with the same rate so I think the statistical assumption is the remaining 20% is done with the same rate.

Sorry for keep bugging you guys with my questions.

No you are not bugging anybody.. We are all here to learn from each other.. I am still not convinced with Kaplan's answer.. and look at duttsit's response just above this post.. and I think he is right.. If we think like the Kaplan is making us think in ST2.. B should be sufficient..
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07 Mar 2006, 13:32
duttsit wrote:

As per explanation for S2,
"number of minutes he spent running" is known (02:30 hrs).
also we know, he had run for "01:15 hrs" at "09:20" (50% of running time). Why can't we calculate the time when he "begun" race (09:20 - 01:15 = 08:05 hrs).

Explanation says "we do not know when he began running.". I guess we do. Wats your take?

I think you are right.. We dont need St1 if we think the way Kaplan wants us to think.. I hope that I will not run into such difficult questions on my real GMAT!
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07 Mar 2006, 16:18
we do need to know when he started the race. so stat 1 together with stat 2 is essential.

duttsit wrote:
bewakoof wrote:
Look at the attachment.. If that does not work.. I will try to explain it in my own words.

btw.. I did get it wrong.. during my practice tests.. I got 5-6 weird questions like these.. my Math score was 40!

As per explanation for S2,
"number of minutes he spent running" is known (02:30 hrs).
how did you get 2.30 hrs withour knowing the 8.05 start time? so stat1 is essential

also we know, he had run for "01:15 hrs" at "09:20" (50% of running time). you know only with the info from stat1 Why can't we calculate the time when he "begun" race (09:20 - 01:15 = 08:05 hrs).

Explanation says "we do not know when he began running.". I guess we do. Wats your take?
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08 Mar 2006, 18:04
I too think statement II is sufficient to answer the question.
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