prorportions: A plane cruises at 180 mph in calm air....

[csolinsky]

A plane cruises at 180 mph in calm air. If the plane flies 7 miles with the wind in the same time as it flies 5 miles against the wind , then what is the wind speed.

7: 5

Need help in setting up this type of problem and some method to learn how to do this

 

[Denis]

Let w = wind speed

with wind: @ (180 + w) ....................7....................> h hours
7 / (180 + w) = h

against wind: @ (180 - w) ................5...............> h hours
5 / (180 - w) = h

OK?

 

[csolinsky]

so if I have this corect then

7/5 = 180+ w / 180-w
7(180- w) = 5 (180 + w)
1260 -7w = 900 + 5w
1260-900 = 5w +7 w
360/ 12 = 12w/ 12
wind speed = 30 milesper hour