Question

Two airplanes leave the airport at the same time, flying in opposite directions. One plane flies 150 miles per hour faster than the other. After 4 hours, they are 2,200 miles apart. What rate are they each flying?

Answer 1

Plane A goes at 200 mph, Plane B goes at 350 mph

Explanation:

What's the speed of those planes?

First, they say they fly in opposite directions, so we assume they are in a straight line, flying away from each other (so, no angles calculations).

They say that plane B goes 150 mph faster than plane A, so

B = A + 150, we'll need this later.

After 4 hours, they are 2,200 miles apart, so in average they grow 550 miles apart each hour (2,200 / 4 = 550).

So, we have plane A and plane B flying, distancing themselves at the average speed of 550 miles per hour, like this: A + B = 550

But we know that B flies faster. Best way to resolve this is to take the last equation and replace B by its value relative to A, like this:

550 = A + B = A + (A + 150) = 2A + 150

So we have 400 = 2A... so A = 200.

Plane A goes at 200 miles per hour, while plane B goes at 350 (200 + 150) miles per hour.