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What Makes A Good Resource - Understand & Ordering Decimals

This page has been archived. The content was correct at the time of original publication, but is no longer updated.
Created on 08 September 2009 by ncetm_administrator
Updated on 03 September 2010 by ncetm_administrator

What Makes a Good Resource

Understanding & Ordering Decimals

Understanding & Ordering Decimals - resource exampleResource description:
A set of cards showing a variety of decimal numbers. Pupils work in pairs on various sorting activities.
Possible ways of sorting could include:
  • Number of decimal places
  • Order of size
  • Numbers that round to 5, 1 and 0
  • Recognisable sequences (some cards would need to be used more than once for this).
Download the resource as a PDF
Teacher comment:
The numbers I’ve chosen should enable pupils to do various sorting activities and also to expose some misconceptions which will give us a chance to talk about them. I have chosen to use cards as I think it will encourage pupils to work together and I am hoping they will be less scared of making mistakes if they can change their mind easily just by moving a card. I also find it much easier to look around the room and get a feeling of what pupils are doing than if they are writing in their books. I’ve constructed the cards so that all pupils will have something they can do and I can work with that.

What I did:
I gave each pair of pupils an envelope with the set of cards in it and asked them to ‘sort out’ the cards in any way they wanted to. One pair asked if they could put the numbers in order and most other pairs took up this idea so that is what I worked with.

As I circulated around the room I used a number of probes or prompts. This helped me to gain some useful insight into what they were thinking and their understanding of decimals. For example, as a result of asking “Do any of these cards have the same value?” I noticed that many pupils did not realise that 5.1 = 5.10. I stopped the group and we discussed this. When they were happy with this idea of decimals looking different but having the same value I then asked each pair to pick out 5 cards and write each one in another way without changing the value (e.g. 5.11 = 5.110).

I noticed that pupils thought that 5.11 > 5.2 because it has more decimal places. I used the counting stick to challenge this by starting at 5.1 and counting in 0.1’s, then starting at 5.11 and counting in 0.01’s etc – always focussing on bridging over ‘the gap’ eg from 5.9 to 6.0 and 6.1 or 5.19 to 5.20 and 5.21

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23 October 2012 13:54
The number with 2 decimal points turned into a good discussion for my group!
By Helenmorg
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22 August 2012 17:39
When I used this I left it in.
It was really interesting watching them trying to fit it into their sorting - gave me lots of info about where to start with the class and who understood place value
By richard
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21 August 2012 22:39
Thank you for sharing this resource and how you used it. Is one of the values meant to have two decimal points, or is that a typo? I wasn't sure if it had a special intended meaning that students could think about.
By daniquinn
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