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# If a car travels with a speed of 40 miles per hour for first

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If a car travels with a speed of 40 miles per hour for first [#permalink]  14 Mar 2007, 02:05
If a car travels with a speed of 40 miles per hour for first 6 hours, and then 60 miles per hour for each additional hour. If during this whole journey it's average speed was 55 miles per hour, how many hours did it travel?
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(40*6+60*x)/x+6=55
240+60x=55x+330
5x=90
x=18

6+18=24
Senior Manager
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Oh....I don't know how I could not see it!

Somehow I wrote it 240+60x=55+330 and got it all wrong.....
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I realized now my mistakes are limited to some silly stuff, solving the Qs correctly but being careless to write all the equations properly.....I must be very vary careful
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