A 13-m long ladder is leaning against a wall. The bottom of the ladder is pulled along the ground, away from the wall, at the rate of 2 m/s. How fast is its height on the wall decreasing when the foot of the ladder is 5 m away from the wall?


Let the original ladder be AC and the pulled ladder be DE


Let AB=y and BC=x


Applying Pythagoras Theorem in ABC


…(1)




Differentiating both sides of eqn (1) wrt to t





1