Application of Number

Level 2

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Estimating Measures - Tutorial 2

This tutorial looks at estimating with rulers, something we all should be familiar with.

Above is an image of part of an ordinary ruler. It is missing the millimetre markings. So the main markings are the cm and the smaller markings are half centimetre (0.5cm).

Let us look at A.

It is between 1cm and 1.5cm. It is definitely over half way and it is close to 1.5 cm.

Let us put the millimetre markings on.

You can see, with the markings, that it is 1.4cm.

This seemed correct from the first image because it was definitely over half way, so it must have been 1.3 or 1.4cm. But it was close to the 1.5cm marker, so it was 1.4cm.

Let us look at B.

It is between 2.5 and 3cm. It is just over half way. Split the space into 5 sections. What do you think B is?

Look at the animation below, which shows the 5 sections put in place.

You can see that B is 2.8cm.

Let us look at the remainder.

C is very close to 4cm. It is 4.1cm.

D is just over 4.5cm. It is 4.6cm.

E is just under half way between 5 and 5.5 cm. It is 5.2cm.

To practise estimating using this scale try this assessment.

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