Question

The diameter of an inflated ball is 18 cm. How many cubic centimetres of air does it contain? What is the surface area of the ball? (π = 3.14)

Answer 1

Radius of sphere (r) = Diameter ÷ 2=18 ÷ 2 = 9 cm
Surface area of a sphere = 4πr²
= 4 × 3.14 × 9 × 9
So, surface area of the ball = 1017.36 sq cm
The volume of air that the inflated ball contains = Volume of sphere =$\frac{4}{3}\mathrm{\pi }{r}^3$
$$\begin{gathered} =\frac{4}{3}\times 3.14\times 9\times 9\times 9 \\ =3052.08\mathrm{cu}\mathrm{cm} \end{gathered}$$