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Measure - Standard units of length (mm, cm, m)

Grade 3IGCSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Understanding millimetres (mm), centimetres (cm), and metres (m) as standard metric units of length.

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Using a ruler correctly by aligning the start of the object with the '0' mark.

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Choosing the appropriate unit: mm for very small objects (seeds), cm for small objects (pencils), and m for larger lengths (room height).

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Relating units: 10 mm make 1 cm, and 100 cm make 1 m.

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Estimating lengths of everyday objects using standard units.

📐Formulae

1 cm=10 mm1 \text{ cm} = 10 \text{ mm}

1 m=100 cm1 \text{ m} = 100 \text{ cm}

Length in mm=Length in cm×10\text{Length in mm} = \text{Length in cm} \times 10

Length in cm=Length in m×100\text{Length in cm} = \text{Length in m} \times 100

💡Examples

Problem 1:

Convert 7 cm into millimetres (mm).

Solution:

70 mm

Explanation:

Since 1 cm=10 mm1 \text{ cm} = 10 \text{ mm}, we multiply the number of centimetres by 10. 7×10=707 \times 10 = 70.

Problem 2:

Which unit would you use to measure the length of a classroom: mm, cm, or m?

Solution:

Metres (m)

Explanation:

A classroom is a large space. Millimetres and centimetres are too small for measuring large distances efficiently, so metres are the most suitable unit.

Problem 3:

A piece of string is 2 m and 15 cm long. What is its total length in centimetres?

Solution:

215 cm

Explanation:

First, convert the metres to centimetres: 2 m=200 cm2 \text{ m} = 200 \text{ cm}. Then, add the remaining centimetres: 200 cm+15 cm=215 cm200 \text{ cm} + 15 \text{ cm} = 215 \text{ cm}.

Problem 4:

An eraser measures 45 mm. How many centimetres and millimetres is this?

Solution:

4 cm and 5 mm

Explanation:

Every 10 mm makes 1 cm. In 45 mm, there are 4 groups of 10 (which is 4 cm) and 5 mm left over.