Rate of change of a side of a square

Question

The rate of a square is increasing at a rate of 28cm per sec. What is the rate of change of the side of the square when it is 7 cm?

______ cm/sec

Answer 1

Perimeter P = 4*s

dP/dt = 4 ds/dt

28 = 4 ds/dt

ds/dt = 1

Perimeter, because the rate is 28 cm per sec...

==============================================

Area would be square centimeters per second

Area A= S^2

dA/dt = 2 S dS/dt

when S=7

28 = 2 * 7 dS/dt

2 = dS/dt