The side of a square is increasing at the rate of 0.2cm/s. The rate of increase of perimeter w.r.t. time is

Perimeter = 4a, where a= side of square
Rate of increase of perimeter w.r.t. time = 4$\frac{\mathrm{da}}{\mathrm{dt}}$ = 4(0.2) =0 .8 cm/s