G21 Estimating measurements and reading scales Boardworks KS3 Maths 2009 G21 Estimating measurements and reading scales G21 Estimating measurements and reading scales This icon indicates the slide contains activities created in Flash. These activities are not editable. For more detailed instructions, see the Getting Started presentation.

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

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

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.

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.

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

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

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

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

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.