# 2. The volume of a cube is increasing at the rate of . How fast is the surface area increasing when the length of an edge is 12 cm?

The volume of the cube(V) =      where x is the edge length of the cube
It is given that the volume of a cube is increasing at the rate of

we can write         ( By chain rule)

- (i)
Now, we know that the surface area of the cube(A) is

- (ii)

from equation (i) we know that

put this value in equation (i)
We get,

It is given in the question that the value of  edge length(x) = 12cm
So,

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