Surface area of sphere radius 1 m

Step by step

The question

Question: find the surface area of a sphere (a ball) with radius 1 m.

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 = 1.

1² means 1 times 1.

That is 1.

So S = 4 × π × 1.

4 times 1 is 4.

So S = 4π.

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.

4 times 3.14 is 12.56.

So the surface area is about 12.56 m².

Let's look back.

First: use the rule.

Last: about how much.