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agasfer [191]
3 years ago
9

A freight train travels at 30 mph. If the freight train is 300 miles ahead of an express train traveling at 55 mph, how long wil

l the express train take to overtake the freight train?
Mathematics
1 answer:
nikdorinn [45]3 years ago
7 0
Let the time elapsed be x, then
30x + 300 = 55x
55x - 30x = 300
25x = 300
x = 300/25 = 12

Therefore, it will take the express train 12 hours to overtake the freight train.
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dA/dx = (1/2)[(-x^2 - x^2 + 361)/(361 - x^2)^(1/2)]

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(-2x^2 + 361)/[2(361 - x^2)^(1/2)] = 0

-2x^2 + 361 = 0

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(19/sqrt(2))^2 + y^2 = 361

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We have maximum area at x = 19/sqrt(2) and y = 19/sqrt(2), or when x = y.
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