Volume of hemisphere radius 2

Step by step

The question

Question: find the volume of a hemisphere (half a ball) with radius 2.

1 Half of a ball

A hemisphere is half of a ball.

A whole ball is 4/3 × π × r³.

π is a special number for circles.

It is about 3.14.

So the hemisphere is half of it: V = ½ × 4/3 × π × r³.

Half of 4 thirds is 2 thirds.

So V = 2/3 × π × r³.

Now put the numbers in: r = 2.

2³ means 2 times 2 times 2.

That is 8.

So V = 2/3 × π × 8.

None of the numbers divides by 3.

So we multiply and keep the 3 at the bottom: 2 times 8 is 16.

So V = 16π over 3.

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.

50.24 divided by 3 is about 16.75.

So the volume is about 16.75 cubic units.

Let's look back.

First: half of a ball.

Last: about how much.