A ladder 15 meters long leans against a vertical wall. If the foot of the ladder is being pulled away from the wall at the rate of 2 meters per minute. How fast is the top of the ladder sliding down the wall at the instant when the foot of the ladder is 12 meters from the wall.

Answer 1

x^2+y^2 = 225
x dx/dt + y dy/dt = 0

now just plug in your numbers and solve for dy/dt