Two cars start moving from the same point. One travels south at 64 mi/h and the other travels west at 48 mi/h. At what rate is the distance between the cars increasing three hours later?

Answer 1

since they start from the same point at the same time, the rate of increase is constant; we have a multiple of the 3-4-5 Pythagorean triple in (48-64-x), so x = 16*5 = 80 mi/hr.