Posted by **joy** on Saturday, July 31, 2010 at 4:51am.

When an airplane flies with a given wind, it can travel 3000 km in 5hrs. When the same airplane flies in the opposite direction against the wind it takes 10hrs to fly the same distance. Find the speed of the plane in still air and the speed of the wind.

- math -
**Reiny**, Saturday, July 31, 2010 at 6:58am
speed of plane in still air --- x km/h

speed of wind ---- y km/h

speed of plane with the wind --- x+y km/h

speed of plane against the wind -- x-y km/h

first fact:

5(x+y ) = 3000

x+y = 600 #1 equation

second fact:

10(x-y) = 3000

x-y = 300 #2 equation

add #1 + #2, it becomes so easy.

- math -
**joy**, Saturday, July 31, 2010 at 11:21am
speed of a plane in still air is 450

speed of wind is 150

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