SOLUTION: Kiran drove from Tortula to Cactus, a distance of 240 mi. She increased her speed by 8 mi/h for the 392 mi trip from Cactus to Dry Junction. If the total trip took 12 h, what was h

Question 1015563: Kiran drove from Tortula to Cactus, a distance of 240 mi. She increased her speed by 8 mi/h for the 392 mi trip from Cactus to Dry Junction. If the total trip took 12 h, what was her speed from Tortula to Cactus?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Kiran drove from Tortula to Cactus, a distance of 240 mi. She increased her speed by 8 mi/h for the 392 mi trip from Cactus to Dry Junction. If the total trip took 12 h, what was her speed from Tortula to Cactus?
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T to C DATA::
dist = 240 miles ; rate = x mph ; time = d/r = 240/x hrs
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C to D DATA:
dist = 392 miles ; rate = x+8 mph ; time = d/r = 392/(x+8) hrs
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Equation:
time + time = 12 hrs
240/x + 392/(x+8) = 12
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240(x+8) + 392x = 12x(x+8)
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240x + 1920 = 12x^2 + 96x
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2x^2 - 144x - 1920 = 0
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x^2 - 72x - 960 = 0
x = 83.5 mph (speed from T to C)
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Cheers,
Stan H.
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