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Question 969048: a jet plane flying with the wind went 2100 mi in 4 h. Against the wind, the plane could fly only 1760 mi in the same amount of time. Find the rate of the plane in calm air and the rate of the wind.
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! a jet plane flying with the wind went 2100 mi in 4 h.
Against the wind, the plane could fly only 1760 mi in the same amount of time.
Find the rate of the plane in calm air and the rate of the wind.
:
let s = the speed of the plane in still air
let w = the rate of the wind
then
(s+w) = effective speed with the wind
and
(s-w) = effective speed against the wind
:
Write an distance equation for each way, (dist = time * speed
4(s+w) = 2100
4(s-w) = 1760
simplify both equations by dividing both sides by 4, use elimination
s + w = 525
s - w = 440
-------------Addition will eliminate w, find s
2s = 965
s = 965/2
s = 482.5 mph is the plane speed in still air
Find w using the first simplified equation
482.5 + w = 525
w = 525 - 482.5
w = 42.5 mph is the rate of the wind
:
:
Confirm this with the 1st original equation
4(482.5 + 42.5) = 2100
4(525) = 2100
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