Question

A 15 ft ladder is leaning against a wall.If the top of the ladder slips down the wall at a rate of 5ft/s, how fast will the foot be moving away from the wall when the top is 9ft above the ground.

Answer 1

x^2 + y^2 = 225

when y = 9
x^2 + 81 = 225
x^2 = 144
x = 12

2 x dx/dt + 2 y dy/dt = 0
24 dx/dt = 18 * 5

Answer 2

3.75