The radius of a circle is increasing uniformly at the rate of 0.3 cent

1.	The radius of a circle is increasing uniformly at the rate of 0.3 centimetre per second. At what rate is the area increasing when the radius is 10 cm? (Take π = 3.14.)
Answer» Consider radius of the circle as r dr/dt = 0.3 cm/s We know that area of the circle = πr² Here the rate of change of area = 2πr dr/dt By substituting the values = 2 × 3.14 × 10 × 0.3 We get dA/dt = 18.84 cm²/s

The radius of a circle is increasing uniformly at the rate of 0.3 centimetre per second. At what rate is the area increasing when the radius is 10 cm? (Take π = 3.14.)

Answer»

Consider radius of the circle as r

dr/dt = 0.3 cm/s

We know that area of the circle = πr²

Here the rate of change of area = 2πr dr/dt

By substituting the values

= 2 × 3.14 × 10 × 0.3

We get

dA/dt = 18.84 cm²/s