# 7.11 Units of volume

Lesson

## Ideas

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.

Apply the idea

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

### 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?

### Examples

#### Example 3

What is the most appropriate unit for measuring the volume of a 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.

### Outcomes

#### MA3-11MG

selects and uses the appropriate unit to estimate, measure and calculate volumes and capacities, and converts between units of capacity