Rate Problem

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Rate Problem

by DCJ » Thu Jul 23, 2009 10:17 pm
I tend to overcomplicate these so someone please explain

How much time did it take a certain car to travel 400km?

(1) The car traveled the first 200 km in 2.5 hours
(2) If the car's average speed had been 20km/hr greater than it was, it would have traveled the 400km in 1 hour less than it did
Source: — Data Sufficiency |

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by yogami » Thu Jul 23, 2009 10:46 pm
IMO B
let the ave speed be x and let the time taken for the 400 km journey be t
so x = 400/t



(1) does not tell us anything about the remaining 200 km so insuff
(2) tells us that x + 20 = 400/(t - 1)

Solving this with the above equation will give us x and t hence suff
200 or 800. It don't matter no more.

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by shibal » Fri Jul 24, 2009 5:29 am
IMO B

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by cholloway » Sat Jul 25, 2009 5:25 pm