Question

If the radius of a circle increases from 3 cm to 3.2 cm, then the increase in the area of the circle is ______ 

Options

• 1.2π cm² 

• 12π cm² 

• 6π cm² 

• 0.6π cm² 

Answer 1

If the radius of a circle increases from 3 cm to 3.2 cm, then the increase in the area of the circle is 1.2π cm².

Explanation:

The area of a circle is A = πR² and `(dR)/dt` = 0.2`

∴ `(dA)/dt = 2piR  (dR)/dt = 1.2 picm^2`