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Lesson 4 of 10
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.
Lesson 4 of 10
New
New
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.
Lesson details
Key learning points
- Small objects are measured in millimetres.
- 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.
Where possible, do this lesson practically using classroom 15 or 30 cm rulers where mm can be seen.
Teacher tip
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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Prior knowledge starter quiz
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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?
I have a piece of ribbon that is 80 cm long. Is this ribbon shorter or longer than one metre?
longer
Q2.Which unit would you use to measure the length of a swimming pool?
Which unit would you use to measure the length of a swimming pool?
mm
cm
kg
Q3.Match the calculation to its answer.
Match the calculation to its answer.
10
80
50
6 x 10
10 x 2
10 x 10
Q4.What is the length of this leaf?
What is the length of this leaf?
Q5.If one metre is equal to 100 cm, how many cm are 6 metres equal to?
If one metre is equal to 100 cm, how many cm are 6 metres equal to?
Q6.Convert the height of this house from centimetres to metres.
Convert the height of this house from centimetres to metres.
800 m
80 m
Assessment exit quiz
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6 Questions
Q1.Which unit of measurement is represented by the shading and arrow in this image?
Which unit of measurement is represented by the shading and arrow in this image?
Centimetres
Metres
Q2.Which of these objects would you measure in millimetres?
Which of these objects would you measure in millimetres?
Length of a football pitch.
Height of a house.
Length of a desk.
Q3.Which is smaller, one centimetre or one millimetre?
Which is smaller, one centimetre or one millimetre?
1 cm
Q4.Is the pebble shorter or longer than 1 cm?
Is the pebble shorter or longer than 1 cm?
shorter
Q5.Starting with the shortest, put these measurements in order of length.
Starting with the shortest, put these measurements in order of length.
Q6.A piece of string is 90 mm long. 2 cm is cut off. What is the length of the piece of string now?
A piece of string is 90 mm long. 2 cm is cut off. What is the length of the piece of string now?