An air traffic controller spots two airplanes at the same altitude converging to a point as they fly at right angles to each other. One airplane is 90 miles from the point and has a speed of 270 miles per hour. The other is 120 miles from the point and has a speed of 360 miles per hour. Exercise (a) At what rate is the distance between the planes changing? Click here to begin! Exercise (b) How much time does the controller have to get one of the airplanes on a different flight path? Step 1 In part (a), it was found that the two planes were 150 miles apart and getting closer at the rate of 450 mph. Distance Use the formula Time = Speed to find the time that the air traffic controller has to get one of the planes on a different flight path. Distance Time = Speed 450 h