Question 214655
If you increase your rate by 25 mph and you are going 25 miles you get there 10 min earlier, what was your initial rate?
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Initial DATA:
distance = 25 miles ; rate = x mph ; time = d/r = 25/x hrs.
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Modified DATA:
distance = 25 miles ; rate = (x+25) mph ; time = d/r = 25/(x+25) hrs.
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Equation:
old time - new time = 1/6 hr
25/x - 25/(x+25) = 1/6
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6*25(x+25) - 6*25x = x(x+25)
150x + 6*625 - 150x = x^2 + 25x
x^2 + 25x - 6*625 = 0
(x-50)(x+75) = 0
Positive solution:
x = 50 mph (initial rate)
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Cheers,
Stan H.