Question

One plane at 520 feet is ascending at a rate of 40 feet per minute. While another plane at 3800 feet is descending at a rate of 120 feet per minute. How long will take the two planes to be at the same altitude?

Answer 1

It takes 20.5 minutes for the two planes to be at the same altitude.

Step-by-step explanation:

Let 't' be time at which the two planes be at the same altitude.

• One plane at 520 feet is ascending at a rate of 40 feet per minute.

⇒ 520 + 40t

• Another plane at 3800 feet is descending at a rate of 120 feet per minute.

⇒ 3800 - 120t

When two plane be at the same altitude,

⇒ 520 + 40t = 3800 - 120t  

⇒ 160t = 3280

⇒ t = 3280/160

t = 20.5 minsutes