SOLUTION: harry drives his car for 15 miles at a certain speed. he then increases his speed by 10 miles per hour and drives for another 20 miles. if the total trip time takes one hour, find

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Question 1133730: harry drives his car for 15 miles at a certain speed. he then increases his speed by 10 miles per hour and drives for another 20 miles. if the total trip time takes one hour, find his original speed.
Answer by josgarithmetic(39616) About Me  (Show Source):
You can put this solution on YOUR website!
           SPEED       TIME        DISTANCE

part1          r         15/r          15

part2         r+10       20/(r+10)     20

TOTAL                    1


15%2Fr%2B20%2F%28r%2B10%29=1-----------solve this for r.