Step by step
The question
Question: what shape is the cut, if we slice a cylinder through the center, up and down?
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 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.
Last: check.