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Year 3

Millimetres as a unit of measure and the relationship between them and cm

I can understand millimetres as a unit of measure and describe the relationship between mm and cm.

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New
New
Year 3

Millimetres as a unit of measure and the relationship between them and cm

I can understand millimetres as a unit of measure and describe the relationship between mm and cm.

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Lesson details

Key learning points

  1. Small objects are measured in millimetres.
  2. There are 10 mm in 1 cm

Keywords

  • Millimetre - A millimetre is a standardised unit of measurement. We can abbreviate millimetre to mm.

Common misconception

Children may think that 10 mm are larger than 1 cm.

There are 10 mm in 1 cm. 1 cm is made up of 10 mm. 10 mm and 1 cm are equivalent in length.


To help you plan your year 3 maths lesson on: Millimetres as a unit of measure and the relationship between them and cm, download all teaching resources for free and adapt to suit your pupils' needs...

Where possible, do this lesson practically using classroom 15 or 30 cm rulers where mm can be seen.
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Licence

This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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6 Questions

Q1.
I have a piece of ribbon that is 80 cm long. Is this ribbon shorter or longer than one metre?
longer
Correct answer: shorter
Q2.
Which unit would you use to measure the length of a swimming pool?
mm
cm
Correct answer: m
kg
Q3.
Match the calculation to its answer.
Correct Answer:1 x 10 = ,10
tick

10

Correct Answer:8 x 10 = ,80
tick

80

Correct Answer:10 x 5 = ,50
tick

50

Correct Answer:60 =,6 x 10
tick

6 x 10

Correct Answer:20 =,10 x 2
tick

10 x 2

Correct Answer:100 = ,10 x 10
tick

10 x 10

Q4.
What is the length of this leaf?
An image in a quiz
Correct Answer: 4 cm, four cm, for cm
Q5.
If one metre is equal to 100 cm, how many cm are 6 metres equal to?
Correct Answer: 600 cm, 600, 6 hundred, six hundred, sixhundred
Q6.
Convert the height of this house from centimetres to metres.
An image in a quiz
800 m
80 m
Correct answer: 8 m

6 Questions

Q1.
Which unit of measurement is represented by the shading and arrow in this image?
An image in a quiz
Correct answer: Millimetres
Centimetres
Metres
Q2.
Which of these objects would you measure in millimetres?
Length of a football pitch.
Height of a house.
Correct answer: Width of a pencil.
Length of a desk.
Q3.
Which is smaller, one centimetre or one millimetre?
1 cm
Correct answer: 1 mm
Q4.
Is the pebble shorter or longer than 1 cm?
An image in a quiz
shorter
Correct answer: longer
Q5.
Starting with the shortest, put these measurements in order of length.
1 - 3 mm
2 - 3 cm
3 - 31 mm
4 - 4 cm
5 - 45 mm
6 - 50 mm
7 - 10 cm
Q6.
A piece of string is 90 mm long. 2 cm is cut off. What is the length of the piece of string now?
Correct Answer: 7 cm, 70 mm, seventy mm, 7 centimetres, 70 millimetres