Question 201093
You drive to houston and back in 8 hours. Suppose your returning speed is 10mph slower than your going speed and that the total trip is 300 miles. What was your speed going to houston?
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Note: Distance to Houston must be 150 miles
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To-Houston DATA:
distance = 150 mi ; rate = x mph ; time = 150/x hrs
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From-Houston DATA:
distance = 150 mi ; rate = x-10mph ; time = 150/(x-10)
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Equation:
time + time = 8 hrs.
150/x + 150/(x-10) = 8
150(x-10) + 150x = 8x(x-10)
300x - 1500 = 8x^2 -80x
8x^2 -380x + 1500 = 0
2x^2 - 95x + 375 = 0
x = [95 +- sqrt(95^2 - 4*2*375)]/4
x = 43.155 mph (rate to-Houston)
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Cheers,
Stan H.
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