Steply

Net of a box 6 by 4 by 3

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 box 6 by 4 by 3, and find its surface area.

box 6 by 4 by 3

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: 6 × 4 is 24.

= top and bottom: 6 × 4 = 24

Front and back: 6 × 3 is 18.

= front and back: 6 × 3 = 18

The two sides: 4 × 3 is 12.

= the two sides: 4 × 3 = 12

Careful!

Count every face in the net.

A box has 6 faces, not 3.

Careful: not 24 + 18 + 12 = 54 ✗

3 Add them all

We add all 6 faces: 108.

= SA = 24 + 24 + 18 + 18 + 12 + 12 = 108

4 Check

Let's check another way.

The faces come in pairs.

One of each: 24 plus 18 plus 12 is 54.

Times 2 is 108.

So the answer is right!

2 × (24 + 18 + 12) = 2 × 54 = 108

Let's look back.

First: unfold it.

Then: area of each face.

Then: add them all.

Last: check.

Answer
= SA = 24 + 24 + 18 + 18 + 12 + 12 = 108

Your turn

Try this one yourself, then check:

box 11 by 4 by 2
Show the answer
148

More from Nets and surface area

The whole lesson: Nets and surface area →