Steply

Net of a cube side 10 cm

Step by step, with the reason for every step · Nets and surface area · Geometry

Step by step

The question

Question: draw the net of a cube, side 10 cm, and find its surface area.

cube, side 10 cm

The surface area is the area of all the outside faces together.

A net shows every face flat.

surface area = all the faces added

1 Unfold it

We cut along some edges and fold it flat.

Matching faces have the same colour.

2 Area of each face

Top and bottom: 10 × 10 is 100.

= top and bottom: 10 × 10 = 100

Front and back: 10 × 10 is 100.

= front and back: 10 × 10 = 100

The two sides: 10 × 10 is 100.

= the two sides: 10 × 10 = 100

Careful!

Count every face in the net.

A box has 6 faces, not 3.

Careful: not 100 + 100 + 100 = 300 ✗

3 Add them all

We add all 6 faces: 600 cm².

= SA = 100 + 100 + 100 + 100 + 100 + 100 = 600 cm²

4 Check

Let's check another way.

All 6 faces of a cube are the same square: 6 times 100 is 600.

So the answer is right!

6 × 10 × 10 = 6 × 100 = 600

Let's look back.

First: unfold it.

Then: area of each face.

Then: add them all.

Last: check.

Answer
= SA = 100 + 100 + 100 + 100 + 100 + 100 = 600 cm²

Your turn

Try this one yourself, then check:

cube, side 6 cm
Show the answer
216 cm²

More from Nets and surface area

The whole lesson: Nets and surface area →