Measure and compare liquid volume in litres

What you will learn

• Measure and compare liquid volume in litres

Models used: number sentences, stories, tables.

Before you start

• Measure and compare mass in grams and kilograms

Compare how much liquid containers hold

Two jugs hold 2 litres and 3 litres. Which holds more?

1. Both bars use the same scale. Compare their lengths and read the names beside them.

   Read the unit with each number. Both measurements use the same unit, so their numbers can be compared.

   Length, mass and liquid volume need suitable units. The scale tells us what each interval or displayed amount represents.

   2 litres2

   3 litres3

   Difference: 1

2. Both bars use the same scale. Compare their lengths and read the names beside them.

   3 litres is the greater measurement. The longer bar represents the larger amount, not a drawing of the object’s shape.

   3 > 2

   2 litres2

   3 litres3

   Difference: 1

3. Both bars use the same scale. Compare their lengths and read the names beside them.

   A litre measures liquid volume. It tells us how much liquid is in the container, not how tall the container looks.

   3 − 2 = 1 litres

   2 litres2

   3 litres3

   Difference: 1

Worked example: A new example, together

One jug measures 7 litres and another 14 litres. What is the difference?

1. Compare readings in the same unit. Read each value with the heading above its column.

   Read the quantity and unit labels before calculating a difference.

   Comparing measurements requires matching the amount and unit.

   Compare readings in the same unit

   First reading	Second reading
   7 litres	14 litres

2. Compare readings in the same unit. Read each value with the heading above its column.

   Both measurements use the same unit.

   Compare readings in the same unit

   First reading	Second reading
   7 litres	14 litres

   One jug measures 7 litres and another 14 litres. What is the difference?

   7 litres

3. Compare readings in the same unit. Read each value with the heading above its column.

   Both measurements use the same unit.

   Compare readings in the same unit

   First reading	Second reading
   7 litres	14 litres

4. Compare readings in the same unit. Read each value with the heading above its column.

   14 − 7 = 7.

   Compare readings in the same unit

   First reading	Second reading
   7 litres	14 litres

5. Compare readings in the same unit. Read each value with the heading above its column.

   The difference is 7 litres.

   Compare readings in the same unit

   First reading	Second reading
   7 litres	14 litres

6. Compare readings in the same unit. Read each value with the heading above its column.

   Check the result against the question we started with.

   Re-read the labels and unit before comparing the numbers.

   We found 7 litres. Comparing measurements requires matching the amount and unit.

   Compare readings in the same unit

   First reading	Second reading
   7 litres	14 litres

Common mistakes to discuss

• Comparing numbers across different units. Change both amounts to the same unit before comparing. 700 g is less than 1 kg, although 700 is the larger number.

Check your understanding

• Measure and compare liquid volume in litres
• choose and interpret units that match the measured quantity
• check the answer against the original quantities and units

Explain your reasoning to an adult, then try a fresh question in the interactive lesson. A result from one attempt is not proof of lasting mastery.