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anne21
Oct 24, 2007, 03:59 PM
To save fuel on the 240km trip to their cottage, the Nakamura family reduce their usual average speed by 20km/h. This lengthens the journey time by 1 hour. What is the slower average speed?

terryg752
Oct 24, 2007, 08:03 PM
All your questions are similar, so am helping with only this one, you should be able to work out others.

Suppose lower speed is x

Then usual speed is x + 20

Change in time : 1 hour, time = distance / speed

Hence 240/x - 240/(x + 20) = 1

Solve this for x