Question

Robin files to San Francisco from Santa Barbara in 3 hours. She files back in 2 hours. If the wind is blowing from the north at a velocity of 40 mph going, but changed to 20 mph from the north returning, what was the airpeed of the Plane Cit's speed in still air)? [francisco is & worth of Santa Barbara]

Answer 1

the wind speed when robin travel from Santa to san Francisco is 40

the wind speed when robin travel from San Francisco to Santa is 20

let the airspeed of the plane is x

when he travels from Santa to san Francisco, the relative airspeed of the plane is x-40

when he travels from San Francisco to Santa, the relative airspeed of the plane is x+20

it is known that the distance between santa and san francisco is contant

so the distance travel by robin will be the same

robin takes 3hr when flies Santa to san Francisco and takes 2 hrs from san Francisco to santa.

so the distance is

3(x-40) = 2(x+20)

3x - 120 = 2x + 40

3x - 2x = 120 + 40

x = 160

sot the air speed of the plane is 160 mph