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?
Let N be the number of minutes when the planes are at the same altitude..so we have
520 +40N = 3800 - 120N add 120N to both sides.....subtract 520 from both sides
160N = 3280 divide both sides by 160
N = 20.5 minutes
