Question

The sides of a square are increasing at the rate of 0.2 cm/sec. When the side is 25cm long, its area is increasing at the rate of ______

Options

• 100 cm²/sec

• 0.10 cm²/sec

• 10 cm²/sec

• 1 cm²/sec

Answer 1

The sides of a square are increasing at the rate of 0.2 cm/sec. When the side is 25cm long, its area is increasing at the rate of 10 cm²/sec.

Explanation:

A = s²

∴ `(dA)/dt = 2 s (ds)/dt`

∴ `((dA)/dt)_{s = 25} = 2 xx 25 xx 0.2 = 10` cm²/sec