Question

If the circumference of a circle increases from 4π to 8π, then its area is

विकल्प

• halved

• doubled

• tripled

• quadrupled

Answer 1

Let the circumference  `C=4pi`

`∴ 2pi r=4pi`

`∴ r=2`

Therefore, area of the circle when radius of the circle is 2 can be calculated as below,

`pir^2=22/7xx4`         .........(1)

Now when circumference is`C=8pi`, then the radius of the circle is calculated as below,

`∴ 2pi r=8pi`

`∴ r=4`

Therefore, area of the circle when radius of the circle is 2 can be calculated as below,

`pi r^2=22/7xx16`

`∴ pi r^2=4(22/7xx4)............(2)`

Therefore, from equation (1) and (2) we can say that its area is quadrupled