1. G21 Estimating measurements and reading scales
Boardworks KS3 Maths 2009
G21 Estimating measurements and reading scales
G21 Estimating measurements and reading scales
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2. G21.1 Estimating measurements
Boardworks KS3 Maths 2009
G21 Estimating measurements and reading scales
G21.1 Estimating measurements

3. G21 Estimating measurements and reading scales
Boardworks KS3 Maths 2009
G21 Estimating measurements and reading scales
Choosing units
What units would you use to measure the following:
The mass of a child
Kilograms
The length of a finger nail
Millimetres
The area of a field
Hectares
The mass of an ant
Milligrams
The distance between two cities
Kilometres
Photo credit: © Shutterstock 2009, gary yim
The capacity of a pool
Litres
The distance between two stars
Light years
The volume of a room
Cubic metres

4. Estimating measurements
Boardworks KS3 Maths 2009
G21 Estimating measurements and reading scales
Estimating measurements
When we estimate measurements we usually compare known measurements to find unknown measurements.
Some useful measurements to know are:
The height of a door is about 2 m.
The mass of a large bag of sugar is 1 kg.
A teaspoon holds 5 ml of liquid.
Most adults are between 1.5 and 1.8 m tall.
A small car weighs about 1 tonne.
Photo credit: © Shutterstock 2009, Freddy Eliasson
Ask pupils to use the height of the classroom door to estimate your height in cm. Ask for estimates of other lengths or weights in the classroom.
The area of a football pitch is 7500 m2.
The capacity of a can of drink is 330 ml.
It takes about 20 minutes to walk 1 mile.

5. Estimating measurements
Boardworks KS3 Maths 2009
G21 Estimating measurements and reading scales
Estimating measurements
Ask pupils to estimate the correct measurement, giving justifications for their answers.

6. G21 Estimating measurements and reading scales
Boardworks KS3 Maths 2009
G21 Estimating measurements and reading scales
G21.2 Reading scales

7. G21 Estimating measurements and reading scales
Boardworks KS3 Maths 2009
G21 Estimating measurements and reading scales
Reading scales
What numbers are the arrows pointing to on the following scale?
2.8 C
3.8 A B
4.4 3 4 5
Each small division is worth
1 ÷ 5 =
0.2
Explain that when reading a scale it is important to start by working out the value of each small division. We do this by taking two consecutive numbered divisions, finding the difference between them and dividing this by the number of small divisions.
Emphasize to pupils that the number of divisions is actually the number of gaps between the lines and not the number of lines themselves.
In this example, we have five divisions between each whole unit. This means that one small division is worth 0.2 units.
A is pointing at
3.8
B is pointing at
4.4
C is pointing at
2.8

8. G21 Estimating measurements and reading scales
Boardworks KS3 Maths 2009
G21 Estimating measurements and reading scales
Reading scales
What numbers are the arrows pointing to on the following scale? C
57.5 C 65 A
72.5 B B 60 70 80
Each small division is worth
10 ÷ 4 =
2.25
In this example, we have four divisions between ten units. This means that one small division is worth 2.25 units.
A is pointing at 65
B is pointing at
72.5
C is pointing at
57.5

9. G21 Estimating measurements and reading scales
Boardworks KS3 Maths 2009
G21 Estimating measurements and reading scales
Reading scales
What numbers are the arrows pointing to on the following scale? C
1.96 A
2.03
2.165 B
2.0
2.1
2.2
Each small division is worth
0.1 ÷ 10 =
0.01
A is pointing at
2.03
B is pointing at
2.165
C is pointing at
1.96

10. G21 Estimating measurements and reading scales
Boardworks KS3 Maths 2009
G21 Estimating measurements and reading scales
Reading scales
Drag the pointer to various positions on the scales and ask pupils to read off the values. Use the pen tool to mark the scales as necessary.