speed of a plane

Question

a helicopter flies 120km with the wind in 30 min. it takes 10 min longer coming back wen they are against the wind. what is the speed of the wind and the helicopter.

Answer 1

Let s be the speed of the helicopter and w=wind speed.

With the wind: (s+w)*30=120

Against the wind (s-w)*40=120

Divide

s + w = 40

s - w = 30

2s=70 => s = 35

Plug 35 into the first equation to get w = 5