 Hong Kong
Stage 2

# Comparisons using volume

Lesson

## Comparing volume

When compare objects by volume, we are comparing the amount of space they take up. A great way to do this is to look at cubes, where all sides measure $1$1 cm. We can put several cubes together and work out the total volume, even with irregular shapes. Let's see how to do this in Video 1.

## Different units of measurement

If we have cubes with sides measured in other units of measurement, such as millimetres (mm), centimetres (cm) and metres (m), we can still compare them by volume. By thinking about how much space each cube would take up, if its sides were $1$1 mm, $1$1 cm or $1$1 m long, we can compare compare objects that have different units of measurement. Not to scale

In Video 2, let's look at how we can work out volume using different units of measurement.

Now we're ready to use what we have seen so far, and compare the volume of objects where both the unit of measurement, and the number are different.

Remember!
• When we are working with the same unit of measurement, we can compare the number.
• When we have different units of measurement, we need to think about how much space each one takes up, so may need to dig a little deeper.

#### Worked Examples

##### Question 1

We want to compare the volumes of the following block stacks.

1. Which block stack is smaller? A B
2. Which block stack has the smaller volume? A B

##### Question 2

Identify the smallest volume measurement from the list:

1. $10$10 m3

A

$10$10 cm3

B

$10$10 mm3

C

##### Question 3

We want to order the following volumes from smallest to largest:

$5$5 cm3, $2$2 m3, $7$7 mm3

1. $7$7 mm3, $2$2 m3, $5$5 cm3

A

$7$7 mm3, $5$5 cm3, $2$2 m3

B

$2$2 m3, $5$5 cm3, $7$7 mm3

C

$5$5 cm3, $2$2 m3, $7$7 mm3

D