Two planes at the same altitude are converging on a point as they fly at a right angle toward each other. One plane is 150 miles from the point and moving 450 mph. The other plane is 200 miles away from the point and moving 600 mph. (a): At what rate is the distance between the planes decreasing? (b):How much time do the planes have before they collide? ....i really need an explanation on this also if anyone is so kind to do so....

Question

Two planes at the same altitude are converging on a point as they fly at a right angle toward each other. One plane is 150 miles from the point and moving 450 mph. The other plane is 200 miles away from the point and moving 600 mph. (a): At what rate is the distance between the planes decreasing? (b):How much time do the planes have before they collide?  ....i really need an explanation on this also if anyone is so kind to do so....