Posted by Anonymous on Tuesday, December 14, 2010 at 8:09pm.
one plane at 520 feet is ascending at the rate of 40 ft per minute, while another plane at 3800 ft is
descending at the rate of 120 ft per minute.
How long will it take the 2 planes to be at the same altitude?

Math  MathMate, Tuesday, December 14, 2010 at 9:51pm
Equate their altitudes in feet and solve for t (in minutes):
520+40t = 3800  120t