Monday, December 5, 2011

How fast can the plane fly in still air?

A small airplane traveling east, with the jet stream, can cover 525 miles in 3 hours. Going west, it takes the plane 7 hours to go the same distance.|||Speed of the wind (y) in terms of speed of the plane (x):


3(x + y) = 7(x - y)


3x + 3y = 7x - 7y


4x = 10y


2x = 5y


y = 2/5x





Speed of plane (x):


3(x + 2/5x) = 525


1 2/5x = 175


7/5x = 175


x = 125





Answer: 125 mph is the speed of plane.

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