A 15 foot ladder is placed against a wall.Suppose the bottom of the ladder slides away from the wall at a constant rate
问题描述：
A 15 foot ladder is placed against a wall.Suppose the bottom of the ladder slides away from the wall at a constant rate of 3 ft.How fast is the top of the ladder sliding down the wall when the bottom is 9 feet from the wall?
Answer
a.- 9/4 ft b.9/4 ft c.-4/9 ft d.None of these
答
b