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NSW SelectiveYear 7 entry

3D shapes and nets for the Selective maths test

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3D shape questions in the Selective maths test ask about faces, edges and vertices, nets, cube counts and views. Your child counts in order, folds a net one face at a time and remembers the hidden faces.

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The full lesson is in the SelectiveReady app. A free account opens How and Why Authors Write; this lesson needs a paid plan.

Updated 16 October 2026 · Facts checked 12 October 2026

3D Shapes & Space (lesson preview)

A short preview from the SelectiveReady lesson “3D Shapes & Space”, on 3d shapes and nets for the NSW Selective test.

Published:

Read the video transcript

So the exam shows you this flat cross-shaped pattern and asks a very direct question. When you fold this thing up, what 3D shape does it actually become? We can solve this every single time with a simple three-step process. First, just count the faces. Easy, we've got six. Step two, what shape are they? They're all identical squares. Now what's the one 3D shape you know that's made of six identical squares? It's the blueprint for a cube, right? And finally, step three, we do our mental fold. We can picture the middle is the base, the sides coming up, and the top folding over perfectly. It works. And just like that, by following those simple steps, we can be 100% confident in our answer. It's a cube.

3D Shapes & Space is a full lesson in the SelectiveReady app. A free account opens one lesson, How and Why Authors Write; the other lessons need a paid plan1SelectiveReady · 13 October 2026 · Published. The preview plays here with English and Chinese captions.

2

What will your child learn in this lesson?

Your child learns to see a flat net as wrapping paper: slice a box along its edges, lay it flat, and that pattern is its net. They'll be able to name the parts of a solid, count them without missing any, fold a net in their head and spot a net that won't work.

The clip folds a cross-shaped net into a cube in three steps. The full lesson adds the main solids, the overlap test and the common traps.

3

How do 3D shapes show up in the Selective maths test?

Solid shape questions sit inside the Mathematical Reasoning section, often with a picture on screen. The Department publishes no topic list, so how many appear isn't known. 2NSW Education · 13 October 2026 · Published

PartThe Department's rule
Questions and time352NSW Education · 12 October 2026 · Published questions in 402NSW Education · 12 October 2026 · Published minutes
Options per question52NSW Education · 12 October 2026 · Published
Working paper23NSW Education · 12 October 2026 · Published sheets, more on request
Wrong answersThe practice papers say there are no marks lost for incorrect answers4NSW Education · 13 October 2026 · Published

Your child can't pick the solid up, so sketching on working paper does the job of hands. Questions draw on concepts from the NSW curriculum up to Year 62NSW Education · 12 October 2026 · Published.

4

What are faces, edges and vertices?

A face is a flat surface, like one side of a dice. An edge is the line where two faces meet, like a crease on a box. A vertex is a corner where edges come together, and two or more are called vertices.

SolidFacesEdgesVertices
Cube6128
Rectangular prism6128
Triangular prism596
Square-based pyramid585
Triangular pyramid464

Count in a fixed order so nothing is missed. For a cube: the top has four edges, the bottom has four, and four more join them.

5

What is the method for net questions?

The lesson's core skill is the mental fold, and its number one rule is to check for overlaps. If two faces would land on the same spot, the net doesn't work.

Fold the net one face at a time: count the faces, pick a base, fold up the sides, then check for overlaps.

  1. Count the faces

    Six faces could make a cube or a rectangular prism. Five could make a triangular prism or a pyramid.

  2. Name their shapes

    Six identical squares means a cube. Triangles at the ends of rectangles means a triangular prism.

  3. Pick a base

    Choose one face to stay on the table. A face in the middle of the net usually works best.

  4. Fold one face at a time

    Lift each neighbour up to meet the base. If two faces overlap, or a side is left open, it isn't a net of that solid.

How can my child tell which faces are opposite?

In a straight line of three squares, the two end squares fold to become opposite faces. A cube has exactly three pairs of opposite faces, and opposite faces never touch.

6

What does a worked net example look like?

We wrote this question to show the line-of-three rule. Here is a cube net drawn as a grid.

E
ABCD
F

Question: When the net folds into a cube, which face is opposite face B?

StepWhat your child does
Check it's a cube netSix squares, no overlaps when folded
Line of three: A, B, CA and C are opposite
Line of three: B, C, DB and D are opposite, so the answer is D
Line of three: E, B, FE and F are opposite
CheckThree pairs, and each face appears once

Faces A, C, E and F are the traps. Each shares an edge with B in the net, so each sits next to B on the cube, never opposite.

7

Which mistakes catch most children?

The most common trap is a mix-up of words: counting faces when the question asks for edges. The other big one is forgetting what can't be seen.

TrapWhat it looks likeThe fix
Faces or edgesAnswering 6 for a cube's edgesFaces are flat, edges are lines, vertices are corners
Hidden cubesCounting only the cubes in viewCount layer by layer, including the back and bottom
Volume or surface areaCounting the cubes inside when the question asks about the outsideInside is volume, the wrapper is surface area
A net with a 2 by 2 blockChoosing a net with four squares in a squareThat block can't fold into a cube
8

Can my child try one on their own?

Here is a cube-counting question from our free maths set. Your child answers it, then checks the steps below.

Practice question · SEL-MA-TST-22

Ivy glued 1 cm cubes together to make this solid block. There are no gaps inside it.

How many cubes did Ivy use?

  1. A

    10

  2. B

    15

  3. C

    22

  4. D

    25

  5. E

    30

Show answer and explanation

Answer: E

Answer: E (30)

  1. The top layer is 5 cubes long and 3 cubes deep: 5 × 3 = 15 cubes.
  2. The block is 2 layers high: 2 × 15 = 30 cubes.

Why the other options are wrong

  • A (10): This adds the length, depth and height (5 + 3 + 2) instead of multiplying.
  • B (15): This counts only the top layer of the block.
  • C (22): This counts only the cubes that can be seen in the picture and misses the 8 hidden cubes.
  • D (25): This adds the 15 squares on top to the 10 on the front, which counts some cubes twice and misses the hidden ones.

  1. Count one layer

    The top layer is 5 cubes long and 3 cubes deep: 5 × 3 = 15 cubes.

  2. Count the layers

    The block is 2 layers high: 2 × 15 = 30 cubes. The answer is E.

  3. Check the trap

    Option C, 22, counts only the cubes in the picture. It misses the 8 hidden ones.

9

How can my child practise 3D shapes at home?

Hands first, then pictures. Building and unfolding real objects makes the mental fold much easier in the test.

Unfold a box

Cut a cereal box along its edges and lay it flat. That's its net. Then fold it back.

Build and sketch

Stack blocks into a shape, then sketch it from the front, side and top.

Draw cube nets

On grid paper, find different six-square nets that fold into a cube. Cut them out to test.

10

Questions parents ask about 3D shapes for Selective

How many nets does a cube have?

There are eleven different nets of a cube. Your child doesn't need to memorise them, only to fold one in their head.

Is a cylinder a prism?

No. A prism has flat faces, while a cylinder has a curved surface and two circle ends.

Does picturing shapes help in Thinking Skills too?

Our Thinking Skills lessons include one on seeing shapes in your mind. It uses the same picture-it skill.

Is the full lesson free?

A free account opens one lesson, How and Why Authors Write; the other lessons need a paid plan1SelectiveReady · 13 October 2026 · Published.

Next questions

Selective Mathematical Reasoning →Lesson: 2D Shapes & Geometry →Lesson: Measurement & Unit Conversions →Selective Thinking Skills →Free Selective practice test →

Sources and checks

  1. SelectiveReady

    SelectiveReady · Checked 13 October 2026

  2. Selective high school practice tests

    NSW Department of Education · Checked 12 October 2026 · Practice materials: personal or non-commercial use only; CC BY 4.0 does not apply (page notice). Page text: CC BY 4.0.

  3. Placement test

    NSW Department of Education · Checked 12 October 2026 · CC BY 4.0 (NSW Department of Education copyright notice); quotes credited

  4. Selective High School Placement Test, Thinking Skills Question Paper, Practice Test 1 (2026 entry practice tests, PDF)

    NSW Department of Education · Checked 13 October 2026 · Practice materials: personal or non-commercial use only; CC BY 4.0 does not apply (page notice). Quoted briefly with credit. Saved text: the cover-page instructions only; the question pages are not stored (W§3.22).

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