SOLUTION: 18. Mark walks 3 miles to the house of a friend and returns home on a bike. He averages 5 mph faster when cycling than walking, and the total time for both trips is 2 hours. Fin

Question 955922:
18. Mark walks 3 miles to the house of a friend and returns home on a bike. He averages 5 mph faster when cycling than walking, and the total time for both trips is 2 hours. Find his walking speed.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Mark walks 3 miles to the house of a friend and returns home on a bike. He averages 5 mph faster when cycling than walking, and the total time for both trips is 2 hours. Find his walking speed.
Walking DATA::
dist = 3 miles ; rate = x mph ; time = d/r = 3/x hrs
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Bike DATA:
dist = 3 miles ; rate = (x+5) mph ; time = 3/(x+5) hrs
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Equation:
time + time = 2 hrs
3/x + 3/(x+5) = 2
3(x+5) + 3x = 2x(x+5)
3x + 15 = 2x^2 + 10x
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2x^2 + 7x - 15 = 0
2x^2 + 10x-3x - 15 = 0
2x(x+5) - 3(x+5) = 0
(x+5)(2x-3) = 0
Positive solution:
x = 3/2 mph (walking rate)
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Cheers,
stan H.
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