Slice a cylinder radius 3 height 8 through the center, up and down

Step by step

The question

Question: what shape is the cut, if we slice a cylinder radius 3 height 8 through the center, up and down, and what is its area?

A cross section is the flat face we see when we slice a solid.

1 Look at the cut

Here is the cylinder.

We slice it through the center, up and down.

The red face is the cut.

2 Name the shape

Flat, the cut looks like this.

Up and down through the center: across, the cut is as wide as the circle; up, as tall as the cylinder.

So it is a rectangle.

Careful!

Not a circle.

Only a cut straight across shows the round part.

3 Find its area

A rectangle's area is length times width: 48.

4 Check

Let's check: look at the cylinder from the side.

You see a rectangle, the same as the cut through the middle.

So the answer is right!

Let's look back.

First: look at the cut.

Then: name the shape.

Then: find its area.

Last: check.