Posted by Anonymous on .
Two commercial airplanes are flying at an altitude of 40,000 ft along straightline courses that intersect at right angles. Plane A is approaching the intersection point at a speed of 427 knots (nautical miles per hour; a nautical mile is 2000 yd or 6000 ft.) Plane B is approaching the intersection at 439 knots.
At what rate is the distance between the planes decreasing when Plane A is 5 nautical miles from the intersection point and Plane B is 5 nautical miles from the intersection point?

Calc 
bobpursley,
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