Question

An air traffic controller is tracking two planes. To start, Plane A is at an altitude of 4385 feet and Plane B is at an altitude of 5000 feet. Plane A is gaining altitude at 55.5 feet per second and Plane B is gaining altitude at 45.25 feet per second.

How many seconds will pass before the planes are at the same altitude?
seconds
What will their altitude be when they're at the same altitude?
feet

Answer 1

60 seconds, 7715 feet

Explanation:

Plane A and B start out 615 feet apart, and we find this by subtracting the height of plane A from plane B, getting 5000-4385=615. Now we have to find how many more feet of altitude plane A is gaining per second over plane B.

To find this we subtract 45.25 from 55.5 and get 10.25 feet per second. Now to find out how many seconds until they'll be at the same altitude we simply divide 615 by 10.25, getting 60 seconds.

For the second part, to find the altitude at this point, we simply multiply the altitude gain of one of the planes per second by the time of 60 seconds to get how much altitude they gained over that time, and add it to the starting altitude. Doing this with plane B we get 45.25*60=2715, and we add that to 5000 to get the final answer of 7715.