Question

Each side of a square is increasing at a rate of 5 cm/s. At what rate is the area of the square increasing when the area of the square is 25 cm2?

Answer 1

A=s^2
da/dt=2sds/dt
we know each side increases at 5cm/s
da/dt=2s(5cm/s)
note, when a=25cm2, s=5cm
so da/dt=2(5cm)(5cm/s)=[50cm2/s]