area of a circle `20 cm^2` then find the radius `?`

The area of a circle is 616cm^(2). Find the radius of the circle.

The area of a circle is 154cm^(2). Find the radius of the circle.

The area of a circle is 616 cm^(2) . Find its radius (in cm).

If the area of a semi-circle is 1925 cm^(2) , then find its radius (in cm).

If the radius of a circle is increasing at a uniform rate of 2 cm/s, then find the rate of increase of area of circle at the instant when the radius is 20 cm.