Question

Sam buys a new ball and he wants to find the surface area of this ball. If the radius of the ball is $4\text{cm}$, then what will be its surface area?

Note: take value of $\pi =\frac{22}{7}$.

• A. $16{\text{cm}}^2$
• B. $50.28{\text{cm}}^2$
• C. $201.14{\text{cm}}^2$
• D. $150.85{\text{cm}}^2$

Answer 1

The correct option is C $201.14{\text{cm}}^2$

A ball is in the shape of a sphere
Let the ball bought by Sam has a centre O and the radius represented as follows:


To find the surface area of this ball, we need to use the surface area of a sphere formula as follows

$\text{Surface area of sphere}=4\pi r^2$,

where $r$ is the radius of the sphere.

Since the radius of the ball is $4\text{cm}$, therefore its surface area is calculated as:

$\begin{array}{cc}\text{Surface area of ball}& =4\pi r^2\\ & =4\left(\frac{22}{7}\right)\left(4^2\right)\\ & =4\times \frac{22}{7}\times 16\\ & =\frac{1408}{7}\\ & =201.14\end{array}$

Hence the surface area of Sam's ball is $201.14{\text{cm}}^2$.