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 it take the two planes to be at the same altitude?

Plane A ascending at height = 520 feets Speed = 40 feet/min Plane B ascending at height = 3800 feets Speed = 120 feet/min Since they are moving towards each other the speeds add up. So Speed = 40 + 120 = 160 Distance would be difference between the two heights So Distance = 3800 - 520 = 3280 Time taken for them to get to same altitude t = D / S Time t = 3280 / 160 = 20.5 minutes