The surface area of a cube is changing at a rate of . At what rate is its volume changing (in cu units per second) when its side is equal to 10 units?
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Let the surface area= S , cubic side= x , and volume= V . Then according to the question,
Now, we need to find the rate of change of its volume with respect to time. That is,
Therefore, when x = 1 0 , its volume will be changing at the rate of 0 . 9 ( 1 0 ) , i.e., 9 cu units per second.