Answer: The rate of change of the distancebetween the bottom of the ladder and the wall at that instant is 6.67 meter per minute.Let us consider that distance between the top of the ladder and the ground is x meterand distance between the bottom of the ladder and the wall is y meter.So, A right angle triangle is formed.Since, the bottom of the ladder is 21 meters from the wall.So, Applying Pythagoras theorem, Given that, the distance between the top of the ladder and the ground is decreasing at 7 meters per minute. Differentiate below equation with respect to time. Thus, the rate of change of the distance between the bottom of the ladder and the wall at that instant is 6.67 meter per minute
Explanation: