# Does it Matter - Measurement

Published over 1 year ago by

This is the third in our 'Does it Matter' series. This week we are looking at common misconceptions and error patterns related to linear measurement.

## 'How long is the caterpillar?'

There are several common answers to this question, and they can each be explained as follows:

- Some students will look at the starting number or the end number on the ruler and say 3 or 14 (units may or may not be named). This is a clear indicator that students do not understand that when we measure we need to look at the start and the finish point not just one of them.
- Some students will notice that the caterpillar 'fills the space' between 4 and 13 and will then count the markers not the spaces which will give the answer 10. This is a clear indicator that they have not understood that when we measure we count the items (units) required to fill the space.
- Students who correctly say â€˜9 centimetresâ€™ are demonstrating that they understand how linear measurement works. Some students will derive the answer by counting the spaces (units) whereas others will find the difference between the numbers 4 and 13.

Download a PDF of the slide here if needed: diM2 Measurement caterpillar PDF

We suggest that you show the slide and ask students to think for a while and then to share their thinking with a partner.

Encourage students to agree, disagree and justify or explain their thinking.

If more provocation is needed to deepen the discussion give them the range of possible answers, 3, 4, 9, 10, 13 and ask them to explain:

- How each answer might have been arrived at,
- What kind of thinking led to those answers,
- Which is the correct answer and how they can prove it.

Your observations of students' conversations and answers will help you to better understand what your students do and don't understand about linear measurement, especially how much they know about using a measuring tool, and what you need to do with them next.

The Follow Up slide has a similar question that will help you check if the discussion generated by the first slide has helped with the possible misunderstandings.

Download a PDF of the slide here if needed: DiM2 Measurement snake PDF

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