Surface area of sphere radius 2 cm

Step by step

The question

Question: find the surface area of a sphere (a ball) with radius 2 cm.

1 Use the rule

Cut the ball in half.

The flat circle inside has area π × r².

The skin of the ball covers exactly 4 of these circles.

Like the peel of an orange.

π is a special number for circles.

It is about 3.14.

So the surface area is S = 4 × π × r².

Now put the numbers in: r = 2.

2² means 2 times 2.

That is 4.

So S = 4 × π × 4.

4 times 4 is 16.

So S = 16π.

We keep π in the answer.

That is the exact answer.

2 About how much

To see about how much, put 3.14 for π.

16 times 3.14 is 50.24.

So the surface area is about 50.24 cm².

Let's look back.

First: use the rule.

Last: about how much.