13. Ship A is 15 miles east of P and is moving west at 20 mph; ship B is 60 miles south of P and is moving north at 15 mph. At what rate is the distance between them changing after 1 hour? Is the distance

increasing or decreasing?

14. Two cars start at same time from the junction of two roads one on each road, with uniform speed v m. p.h. If the roads are inclined at 120°, show that the distance between them increases at the rates of√3 v. m.p. h.