SOLUTION: A man drove 156 miles at a constant rate. If he had driven 5 miles per hour faster he would have made the trip in 12 minutes less time. How fast did he drive?
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Question 897020: A man drove 156 miles at a constant rate. If he had driven 5 miles per hour faster he would have made the trip in 12 minutes less time. How fast did he drive? Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! A man drove 156 miles at a constant rate. If he had driven 5 miles per hour faster he would have made the trip in 12 minutes less time. How fast did he drive?
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Original DATA:
distance = 156 miles ; rate = x mph ; time = d/r = 156/x hrs
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New Conditions::
distance = 156 miles ; rate = (x+5) mph; time = d/r = 156/(x+5) hrs
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Equation::
Note: 12 minutes = 1/5 hr
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156/x - [156/(x+5)] = 1/5 hr
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156(x+5) - 156x = (x(x+5)/5
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156*5*5 = x^2 + 5x
x^2 + 5x - 3900 = 0
x = 60 mph
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Cheers,
Stan H.
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