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Windows and Overlays – 2<br />
Windows can be made to overlay on<br />
number grids such as a 1–100 grid.<br />
The window shown on the right<br />
produces an ‘add 19’ pattern. If you<br />
add nineteen to the smaller<br />
number the larger number will be<br />
produced. It does not matter<br />
where the window is overlaid on<br />
the grid.<br />
Try making the following windows out of grid paper. Shade the squares on the grids below to<br />
show where you will have to cut.<br />
1. +11 window<br />
2. +3 window<br />
3. +8 window<br />
4. +12 window<br />
Challenge: Make a number window for the multiples of nine. Overlay it on a 1–100 grid, and<br />
rotate 90º (or 1 / 4 of a turn).<br />
What do you notice?<br />
What about other multiples?<br />
R.I.C. Publications www.ricgroup.com.au<br />
57<br />
<strong>Number</strong> <strong>Grids</strong><br />
ISBN 978-1-86311-826-2
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