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GMAT Prep ?? (Helen)

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GMAT Prep ?? (Helen)

by dferm » Sun May 04, 2008 3:15 pm
How many hours did it take Helen to drive from her house to her parents' house?

(1) Helen's average speed on this trip was 72 kilometers per hour
(2) If Helen's average speed on this trip had been 8 kilometers per hour greater, it would have taken her 1 hour less.
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Source: — Data Sufficiency |
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by codesnooker » Mon May 05, 2008 12:47 am
This is very simple question based on formula, Distance = Speed * time.

Answer is (C).

I would like you to solve it on your own. Solving it on own will increase your logical ability. I have told the formula to be used. If you still didn't get it. Let me know, I will explain it.
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by dferm » Mon May 05, 2008 5:30 am
I kind of get the question but still confused with the one hour less....

Just throw a little light on it...
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by dferm » Mon May 05, 2008 5:32 am
Plus what is my distance...do we pick a smart number for it...
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by codesnooker » Mon May 05, 2008 5:47 am
Okay let me try to explain it to you.

Formula to be used: Distance = Time X Speed.

For the statement (1),

We know that Speed = 72 KM/Hr
and lets say time taken = t hours

So Distance = (72 X t) Km

Now from Statement (2),

Speed = (72 + 8) KM/Hr
Time = (t - 1) hours

Distance = (72 + 8) (t - 1) Km

So, as you know that the distance between the her house and her parent's house is never going to be changed. So we can equate both the above equations.

That is, 72t = 80 (t-1)

Now because its a linear equation of one variable, so now you can derive the value of t. Once you know the value of t, you can get the distance also.

As it is a DS question, no need to solve further. However, just for your sake of information, I am doing further calculations:-

72t = 80t - 80
8t = 80
t = 10 hours
Distance = Speed X time
Distance = 72 X 10 = 720 Km

Let me know, if there is still confusion. Remember the formula for the future questions.
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by dferm » Mon May 05, 2008 6:27 am
There was where my confusion was at...in the part of equated the two equations...

Thanks a billion....
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by san2009 » Wed Jul 21, 2010 3:06 am
what is the OA?
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by gmatmachoman » Wed Jul 21, 2010 3:28 am
san2009 wrote:what is the OA?
C only bhai!!
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