SOLUTION: against the wind a small plane flew 21 miles in 1 hr and 10 minutes, the return trip only took 50 minutes. what was the speed of the wind, what was the speed of the plane in still

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Question 422162: against the wind a small plane flew 21 miles in 1 hr and 10 minutes, the return trip only took 50 minutes. what was the speed of the wind, what was the speed of the plane in still air
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
against wind 1 1/6 hours
with wind 5/6 hours

Distance = same= 21 miles
plane speed =x
wind speed =y
t=d/r
21/(x-y)=1.17
1.17(x-y)=21.00
1.17x-1.17y=21 ....................1
21/(x+y)= 5/6
5/6(x+y )=21
5/6x+ 5/6y=21 ...............2
Multiply (1) by 5
Multiply (2) by 8
we get
5.83x-5.83y=105
6.67x+6.67y=168
12.5x=273
/12.5
x=21.84 mph plane speed

plug value of x in (1)
1.17x-1.17y=21
25.48-1.17y=21
-1.17y=21-25.48
-1.17y=-4.48
y=3.84 mph wind speed