Question 706061
Thelma's average driving speed is 15 miles per hour faster than Kirk's. in the same length of time it takes Thelma to drive 114 miles, Kirk only drives 84 miles. What is Thelma's average driving speed?
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Kirk DATA:
rate = x mph ; distance = 84 miles ; time = d/r = 84/x hrs
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Thelma DATA:
rate = x+15 mph ; distance = 114 miles ; time = d/r = 114/(x+15)
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Equation:
time = time
84/x = 114/(x+15)
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Cross-multiply:
114x = 84x + 84*15
30x = 84*15
x = (1/2)84
x = 42 mph (Kirk's rate)
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x + 15 = 57 mph (Thema's rate)
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Cheers,
Stan H.
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