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Marla travels

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Marla travels

by mjjking » Mon Mar 23, 2009 11:11 pm
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any help welcome!!
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by bluementor » Tue Mar 24, 2009 3:59 am
Total time actually taken = T
Total time taken if average speed is x = T'

Question stem: T/T' = ?

T = y/x + (40-y)/(1.25x)
T = y/x + (40-y)/(5x/4)
T = 5y/5x + 4*(40-y)/5x
T = (5y + 160 - 4y)/5x
T = (y + 160)/5x

Hypothetical situation (if Marla travelled the 40 mile trip at an average speed x):

T' = 40/x

Therefore:
T/T' = ((y + 160)/ 5x)/(40/x) = (y + 160)/(40*5)

Notice that x has been cancelled off. So we only need to know y. Hence B.

-BM-
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