Question

The side of a square is increasing at the rate of 0.5 cm/sec. Find the rate of increase of the perimeter when the side of the square is 10 cm long.

Answer 1

If x cm is the side of the square and p cm is the perimeter, then p = 4x

Differentiating w.r.t. t, we get

`(dp)/dt = 4dx/dt`  ....(1)

Now `dx/dt` = 0.5 cm and x = 10 cm

∴ From (1): `(dp)/dt` = 4(0.5)

= 2 cm/sec.