Question

A plane is traveling 600 miles. It takes the plane 5 hours against the wind and 4 hours with the wind. What is the speed of the plane in still air, and what is the speed of the wind?

Answer 1

Answer: the speed of the plane in still air is 135 miles per hour

the speed of the wind is 15 miles per hour

Step-by-step explanation:

Let x represent the speed of the plane in still air

Let y represent the speed of the wind.

The distance travelled by the plane is 600 miles.

Distance travelled = speed × time

It takes the plane 5 hours against the wind. This means that the total speed is (x-y) miles per hour. Therefore,

600 = 5(x- y) = 5x - 5y - - - - - - - 1

It takes the plane 4 hours with the wind. This means that the total speed is (x+y) miles per hour. Therefore,

600 = 4(x+ y) = 4x + 4y - - - - - - - - 2

Multiplying equation 1 by 4 and equation 2 by 5, it becomes

2400 = 20x - 20y

3000 = 20x + 20y

Adding both equations

5400 = 40x

x = 5400/40 = 135

Substituting x = 135 into equation 1, it becomes

4 × 135 + 4y = 600

540 + 4y = 600

4y = 600 - 540 = 60

y = 60/4 = 15