Measuring lengths in cm and mm

The Maths Habit

Which line is longer, A or B?

AB

They are the same length. Our eyes are easy to fool, so we measure.

Centimetre (cm)
A unit of length. One centimetre is 10 millimetres.
Millimetre (mm)
A small unit of length, the smallest marks on a ruler.
Length
How long something is, from one end to the other.

012345cm
  1. Start at 0.Not at the end of the ruler: the 0 is a little way in.
  2. Read the whole centimetres.The last number the line passes.
  3. Count the millimetres after them.4 cm 3 mm is 4.3 cm, or 43 mm.

How many millimetres make 1 centimetre?

1 cm = ? mm 10 mm

Does this line start at 0?

012345cm No: it starts 5 mm before the 0

How long is the line? Start at 0. Read the whole centimetres. Count the millimetres after them. 3.8 cm

012345cm
3 cm 8 mm = 3.8 cm

How long is the line? Start at 0. Read the whole centimetres. Count the millimetres after them. 2.1 cm

012345cm
2 cm 1 mm = 2.1 cm

How long is the line? Start at 0. Read the whole centimetres. Count the millimetres after them. 3.8 cm

012345cm
3 cm 8 mm = 3.8 cm

How long is the line? Start at 0. Read the whole centimetres. Count the millimetres after them. 4.6 cm

012345cm
4 cm 6 mm = 4.6 cm

How long is the line? Start at 0. Read the whole centimetres. Count the millimetres after them. 3.8 cm

012345cm
3 cm 8 mm = 3.8 cm

How long is the line? Start at 0. Read the whole centimetres. Count the millimetres after them. 3.3 cm

012345cm
3 cm 3 mm = 3.3 cm

How long is the line? Start at 0. Read the whole centimetres. Count the millimetres after them. 3.8 cm

012345cm
3 cm 8 mm = 3.8 cm

How long is the key? Start at 0. Read the whole centimetres. Count the millimetres after them. 4.7 cm

012345cm
4 cm 7 mm = 4.7 cm

How long is the line? Start at 0. Read the whole centimetres. Count the millimetres after them. 3.8 cm

012345cm
3 cm 8 mm = 3.8 cm

This line starts at 1 cm. How long is it? Start at 0. Read the whole centimetres. Count the millimetres after them. 3.2 cm

012345cm
3 cm 2 mm = 3.2 cm

Measuring lengths in cm and mm worksheet, page 1

012345cm
  1. Put the 0 on the dot.
  2. Count along to the length.The whole centimetres, then the millimetres.
  3. Mark it and join it to the dot.Draw along the edge of the ruler.

Write 3 cm 5 mm in centimetres.

3 cm 5 mm 3.5 cm

Write 28 mm in centimetres.

28 mm 2.8 cm

Draw a line 4.3 cm long. Put the 0 on the dot. Count along to the length. Mark it and join it to the dot. 4 cm 3 mm

012345cm

Draw a line 2.6 cm long. Put the 0 on the dot. Count along to the length. Mark it and join it to the dot. 2 cm 6 mm

012345cm

Draw a line 4.3 cm long. Put the 0 on the dot. Count along to the length. Mark it and join it to the dot. 4 cm 3 mm

012345cm

Draw a line 3.7 cm long. Put the 0 on the dot. Count along to the length. Mark it and join it to the dot. 3 cm 7 mm

012345cm

Measuring lengths in cm and mm worksheet, page 2

Answer sheet

Thumbs up: right. Thumbs down: wrong.

  1. 6 cm 3 mm = 6.3 cm

    Right

  2. 45 mm = 45 cm

    Wrong: 4.5 cm

  3. 2.8 cm = 28 mm

    Right

  4. 7 cm 5 mm = 7.05 cm

    Wrong: 7.5 cm

  1. A line is 3.6 cm long. Another line is 18 mm longer. How long is the second line?

    5.4 cm

  2. Draw a square with sides 2.5 cm. How far is it all the way round, in mm?

    100 mm

  3. A broken ruler starts at 3 cm. A pencil reaches from the 3 to 10.2. How long is the pencil?

    7.2 cm

  1. How long is the line?

    4.8 cm
    012345

  2. The line starts at 1 cm. How long is it?

    4.5 cm
    0123456

  3. Draw a line 3.6 cm long in the space.

    a line 3.6 cm long
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