Question

1. In the adjoining figure, the area enclosed between the concentric
circles is 770 cm. If the radius of the outer circle is 21 cm,
calculate the radius of the inner circle.

Answer 1

Respuesta:

Radius of the inner circle = 13.996 cm

Explicación paso a paso:

Please, next time include the figure.

The area of a circle is: A = π r²

The area of the outer circle is:

A = π r² = π * 21² = 441 π

The area of the inner circle is:

A = π r²

You want to calculate this radius.

The area enclosed between the concentric circles = area of the outer circle - area of the inner circle:

770 = 441 π - π r²

770 - 441 π = - π r²

-615.44 = - π r²

-615.44 / -π = r²

195.90 = r²

r = sqrt (195.90) = 13.996