binh

Two aeroplanes fly eastwards on parallel courses 12 miles apart. One flies at 240 m.p.h. and the other at 300 m.p.h. How fast is the distance between them changing when the slower plane is 5 miles farther east than the faster plane?

A ladder rests against a vertical pole. The foot of the ladder is sliding away from the pole along horizontal ground. Find the inclination of the ladder to the horizontal at the instant when the top of the ladder is moving 3 times as fast as the foot of t...