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Distance of the car

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Distance of the car

by zagcollins » Mon Jul 28, 2008 9:13 am
How much time did it take a certain car to travel 400 km?
1) The car traveled the first 200km in 2.5 hours
2) If the car's average speed had been 20km per hour greater than it was, it would have traveled the 400km in 1hr less time than it did

OA is B...ricky is right...its a GPREP question...can sum1 pls elaborate a 'lil further?
Last edited by zagcollins on Tue Jul 29, 2008 3:52 am, edited 1 time in total.
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by agent47 » Mon Jul 28, 2008 9:23 am
IMO E what is OA ?
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by ricky » Mon Jul 28, 2008 9:42 am
IMO B.

Let x be the average Speed.

400/(x +20) =400/x -1

Solve for x
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by augusto » Mon Jul 28, 2008 12:06 pm
I think it's E

ricky, check that in your equation if X is the average Speed, you can substract 20km/h (which is also a speed), but you can't substract 1h.
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by spring » Fri Aug 01, 2008 7:28 am
augusto wrote:I think it's E

ricky, check that in your equation if X is the average Speed, you can substract 20km/h (which is also a speed), but you can't substract 1h.
I think ricky means [(400/x) - 1] (not 400/(x-1)) because 400/x is the time with speed x, but it should be subtracted 1h in order to consistent with speed (x+20). And he's right.
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