question_answer 10)

A ladder 5 m long is leaning against a wall. The bottom of the ladder is pulled along the ground, away from the wall, at the rate of 2 cm/s. How fast is its height on the wall decreasing when the foot of the ladder is 4 m away from the wall ? 

Answer:

Let BC is the ladder 5 m long.                x = distance of foot of ladder from foot of the wall.       h = height of top of ladder on the wall.       Given :                       ?. (1)       Now in right angled             x2 + h2 = 25                               ?. (2)             [Using (1)]                               [Using (2) x = 4  h = 3]                    Height of top of the ladder on the wall decreases at the rate