Topics
11. 3D Measurement
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Australia
Year 6

11.02 Units of volume

Lesson
Practice
Lesson

Are you ready?

Estimating the  length of objects  can help us in this lesson. Let's try a problem to review.

Examples

Example 1

Choose the best estimate for the length of a fingernail.

A
100 millimetres
B
60 millimetres
C
10 millimetres
D
1 millimetre
Worked Solution
Create a strategy

Use a ruler. The gap between each line is 1 millimetre.

A ruler showing the gap between 0 and small line next to it measures 1 millimetre.
Apply the idea

A sultana has almost the same length of a fingernail. We can see below that a sultana is 9 millimetres.

A ruler showing a sultana measures 9 millimetres.

The closest estimate from the options is 10 millimetres, so the answer is option C.

Idea summary

To estimate the length of an object, we can compare it to an object where we have an idea already of its estimated length.

Units for volume

Let's look at the units for volume of \text{mm}^3, \text{cm}^3, and \text{m}^3.

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Examples

Example 2

Which of these is the bigger volume?

A
1 \text{ mm}^3
B
1 \text{ cm}^3
Worked Solution
Create a strategy

Since the options have the same number, choose the option with the bigger unit.

Apply the idea

We know that centimetres \text{(cm)} is bigger than millimetres \text{(mm)}, so the answer is option B.

Idea summary

Units of volume from smallest to biggest: \text{mm}^3, \text{cm}^3, and \text{m}^3.

Choose units of volume

How do you know which unit to use?

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Examples

Example 3

What is the most appropriate unit for measuring the volume of a box?

An open box
A
\text{ cm}^3
B
\text{ mm}^3
Worked Solution
Create a strategy

Think about what type of objects would be measured by these units.

Apply the idea

\text {mm}^3 is useful to measure a drop of liquid, or the volume of a coin and other tiny objects. \text {cm}^3 is useful to measure bigger objects like a ball or a box.

So, the answer is option A.

Idea summary

A cubic millimetre \left(\text{mm}^3\right) is about as big as a grain of sand.

A cubic centimetre \left(\text{cm}^3\right) is about as big as the end of your thumb.

A cubic metre \left(\text{m}^3\right) is about as big as a washing machine.

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