SOLUTION: tera traveled 120 miles at a certain speed. tara then drove another 100 miles at a speed that was 10 mph slower. If the total time of taras trip was 4 hours, what was her speed at

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: tera traveled 120 miles at a certain speed. tara then drove another 100 miles at a speed that was 10 mph slower. If the total time of taras trip was 4 hours, what was her speed at       Log On

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Question 724036: tera traveled 120 miles at a certain speed. tara then drove another 100 miles at a speed that was 10 mph slower. If the total time of taras trip was 4 hours, what was her speed at each part of the trip
Answer by stanbon(75887) About Me  (Show Source):
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tera traveled 120 miles at a certain speed. tara then drove another 100 miles at a speed that was 10 mph slower. If the total time of taras trip was 4 hours, what was her speed at each part of the trip
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1st leg DATA:
distance = 120 miles ; speed = x mph ; time = 120/x hrs
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2nd leg DATA:
distance = 100 miles ; speed = x-10 mph ; time = 100/(x-10) hrs
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Equation:
120/x + 100/(x-10) = 4 hrs
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Modify:
30/x + 25/(x-10) = 1
30(x-10) + 25x = x^2-10x
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x^2 -10x - 55x + 300 = 0
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x^2 - 65x +300 = 0
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(x-60)(x-5) = 0
Positive useful solution:
x = 60 mph
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Cheers,
Stan H.
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