SOLUTION: Noah makes a round trip commute to work each day by car. His trip in the morning is quicker because he leaves before traffic gets bad, so his speed is 15 miles per hour faster in t

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Question 1131522: Noah makes a round trip commute to work each day by car. His trip in the morning is quicker because he leaves before traffic gets bad, so his speed is 15 miles per hour faster in the morning which makes his 8 mile commute take 30 minutes less time on the way home when traffic is bad and he drives more slowly.
What's Noah's average speed in both directions?
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
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..., 15 miles per hour faster in the morning which makes his 8 mile commute take 30 minutes cross%28less%29 MORE time on the way home,...
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                SPEED            TIME          DISTANCE

GOING            r+15            8/(r+15)       8

RETURN           r               8/r            8

DIFFERENCE                       1/2

8%2Fr-8%2F%28r%2B15%29=1%2F2------solve for r.