Question

Inner radius of a hollow iron sphere is 9 cm. If Iron is 1 cm thick, find the volume of iron used to make the ball.

• A. 1155.08 cm³
• B. 1156.08 cm³
• C. 1134.59 cm³
• D. 1133.58 cm³

Answer 1

The correct option is C

1134.59 cm³

Thickness of the iron = 1 cm

Inner radius = 9 cm

Therefore, inner volume of sphere = $\frac{4}{3}$ (${\pi r_{inner}}^3)$ = $\frac{4}{3}$ (${\pi 9}^3)$ = 3052.08 ${cm}^3$

Outer radius = 10 cm.

Outer volume = $\frac{4}{3}$ (${\pi r_{outer}}^3)$= $\frac{4}{3}$ (${\pi 10}^3)$ = 4186.67 ${cm}^3$

Then, iron used = outer volume – inner volume = 1134.59 ${cm}^3$