Straight Line Graphs: NRich Diamond Collector

I’ve used the excellent NRich resource Diamond Collector as consolidation of work on straight line graphs before with a Year 7 top set. I’m wanting to use this resource with a Year 9A set when I (a) don’t have access to a computer suite and (b) want the work to be a bit more involved and rigorous.

Using screenshots I have created 15 different boards so that pupils can work in pairs. I will laminate these so that pupils can use drywipe markers to write their equations in the blue boxes. By removing this task from the ICT version it will ensure that pupils are having a chance to actually draw their lines and hence find the equation of their chosen line, rather than the applet plotting it for them. As a plenary, pairs will swap boards and:

1) Check the lines stated are plotted correctly on the grid

2) Count the number of diamonds collected by the three lines

3) Suggest possible equations of lines which would collect more diamonds, if possible.

I suggested this in our joint-planning meeting tonight and we came up with a novel way for pupils to decide where best to position their straight line in order to collect the maximum number of diamonds, deciding string was too “floppy”, we’ve opted to give pupils spaghetti which they can poistion and re-position on the axes before drawing in the lines of their choice!

I’ll be using this next week with pupils and will update the post then to let you know how it goes…


This worked exceptionally well. Things to look out for in retrospect:

This way of presenting the task probably works best with more able pupils as allowing pupils to position the lines wherever they like leads to some tricky gradient calculations. In addition it is possible to position the line so that the y-intercept lies off the grid. My A set pupils enjoyed the challenge of working out where this would be. With a different set I may be tempted to say that the y-intercept has to be within the confines of the grid. Pupils enjoyed the competitive elements. Particularly as I bribed them with one team point per diamond! The spaghetti worked well as a temporary line.




  1. Alison · January 11, 2012

    Really glad you are finding our NRICH resources useful. Would you mind if I linked your PowerPoint to the Teachers’ Notes of Diamond Collector so that other teachers can use it? I would of course include a link to your blog.

    • ideasfortheclassroom · January 11, 2012

      No. That’s fine I put it there to be of use to people šŸ™‚

      • Alison · January 12, 2012

        Great! We’re in the process of updating the interactivity for Diamond Collector, I’ll send you a sneak preview once we’ve uploaded the new version.

      • Alison · January 20, 2012

        The new version is online now at, would love to know what you think of the changes!

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