198) How Much Speed

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198) How Much Speed

by ern5231 » Mon May 17, 2010 1:45 am
A person takes 18 minutes to run 5 kms. The first two kilometers are run at 20 km/hr. what is the average speed for remaining 3 km?

My answer is working out to be 15 km/hr. Can anyone confirm?

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by rajeshsources » Mon May 17, 2010 2:48 am
ern5231 ----

5KM in 18 Minutes(18/60 hours= 3/10 hours)

He ran 2 KM with speed of 20km/hr, then time taken for him = T = D/S = 2/20 = 1/10 hour

Time remain = (3/10) - (1/10) = 2/10 hour

So, the speed for remaining 3 KM = Distance(remain)/Time(remain) = 3*10/2 = 3*5 = 15 Km/hour.


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