Steply

Net of a cube side 5

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 5, and find its surface area.

cube, side 5

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: 5 × 5 is 25.

= top and bottom: 5 × 5 = 25

Front and back: 5 × 5 is 25.

= front and back: 5 × 5 = 25

The two sides: 5 × 5 is 25.

= the two sides: 5 × 5 = 25

Careful!

Count every face in the net.

A box has 6 faces, not 3.

Careful: not 25 + 25 + 25 = 75 ✗

3 Add them all

We add all 6 faces: 150.

= SA = 25 + 25 + 25 + 25 + 25 + 25 = 150

4 Check

Let's check another way.

All 6 faces of a cube are the same square: 6 times 25 is 150.

So the answer is right!

6 × 5 × 5 = 6 × 25 = 150

Let's look back.

First: unfold it.

Then: area of each face.

Then: add them all.

Last: check.

Answer
= SA = 25 + 25 + 25 + 25 + 25 + 25 = 150

Your turn

Try this one yourself, then check:

cube, side 2
Show the answer
24

More from Nets and surface area

The whole lesson: Nets and surface area →