speed in still air

unique · 2006-12-21 10:24:07

A fighter plane could fly at 4 times the speed of the wind. as a result, it could travel 60 miles downwind in 1 hour longer than it took to travel 300 miles upwind. what waas the fighter plane's speed in still air?

John E. Franklin · 2006-12-21 10:57:12

I think you have upwind and downwind mixed up, or else I have their definitions messed up.
Downwind is with the wind I thought, and upwind is against the wind.

unique · 2006-12-21 11:25:35

OH MY GOD i messed it up.....
i had to write.... 600 instead of 60
A fighter plane could fly at 4 times the speed of the wind. as a result, it could travel 600 miles downwind in 1 hour longer than it took to travel 300 miles upwind. what waas the fighter plane's speed in still air?

But the upwind and downwind thing is right.

John E. Franklin · 2006-12-21 12:07:09

Let's see, uh, 5 times wind speed times (uptime + 1) = 2 (3 times wind speed times uptime).
600 = 5w(u+1) = 6wu
600 = 5wu + 5w = 6wu
Make into 2 equations and subtract 5/6ths of equation from the other and
solve for w, the wind speed.
100 = 5w
wind speed = 20mph
plane speed = 80 in still air.
Didn't check answer. You can. (as Krassi would say)

Math Is Fun Forum

#1 2006-12-21 10:24:07

speed in still air

#2 2006-12-21 10:57:12

Re: speed in still air

#3 2006-12-21 11:25:35

Re: speed in still air

#4 2006-12-21 12:07:09

Re: speed in still air

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