If the surface area of a cube is increasing at a rate of , retaining its shape; then the rate of change of its volume (in ), when the length of a side of the cube is 10 cm , is:
- (A)9✓ Correct
- (B)18
- (C)10
- (D)20
Answer: (A)
Solution
With surface area , differentiating gives , so at the edge grows at . The volume then changes at .
JEE Main · 2020 · 03 Sep 2020 · Shift 2 · Single correct option