SOLUTION: a man drives his car for 150 km travelling at his normal average speed. if he increases his speed by 10 km/h, he will arrive half an hour sooner. what is his original average speed

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Question 1158833: a man drives his car for 150 km travelling at his normal average speed. if he increases his speed by 10 km/h, he will arrive half an hour sooner. what is his original average speed?
Answer by josgarithmetic(39616) About Me  (Show Source):
You can put this solution on YOUR website!
              SPEED         TIME        DISTANCE

ORIGINAL         r          150/r         150

FASTER          r+10        150/(r+10)    150

DIFFERENCE                  1%2F2

150%2Fr-150%2F%28r%2B10%29=1%2F2