Interactive 100 Square
Number · Year 1–Year 5
Shade, hide and reveal. Multiples, patterns and percentages.
About the 100 square
Tap squares to shade them, or drag across the grid to shade a whole run at once. Dragging is much quicker than tapping when you are counting in steps.
The step buttons shade every multiple in one go. Put the 5s in one colour, then the 3s in another, and the multiples of 15 end up in the second colour. That is usually enough for a class to start describing the pattern before anyone names it.
Hide the numbers to turn the same grid into a blank hundred square for estimating and positioning, then reveal them to check.
Three grids are available. The usual 1 to 100, a 1 to 120 for crossing the hundred, and a 0 to 99 where every column shares a units digit and every row shares a tens digit.
Tap % and the shaded part is read four ways at once: 50 out of 100, a half, 50% and 0.5. None of the four is worked out from another, so the board cannot show a percentage that disagrees with its own decimal, and a class that has seen half a grid being all four things at the same time has a picture to fall back on rather than a rule about moving the decimal point.
The readings need a hundred squares, so the % button greys out on the 1 to 120 grid: forty-seven of a hundred and twenty squares is not forty-seven per cent, and a board that said so would be teaching the one thing percentages are for. Hide the numbers first for the best version of it, and the grid becomes an area to shade and read off.
How to use it on your whiteboard
- 1Tap a square to shade it. Tap it again to clear it.
- 2Drag across several squares to shade them together. That counts as one action, so one Undo clears the lot.
- 3Pick another colour to shade a second pattern over the first.
- 4Tap a step button, 2s through to 10s, to shade all its multiples. Tap it again to clear them.
- 5Use Hide for a blank grid, then Show to reveal the numbers and check.
- 6Tap % to read the shaded part as a fraction, a percentage and a decimal.
Questions
- Can I show a 120 square?
- Yes. One tap switches between 1 to 100, 1 to 120 and 0 to 99.
- Can children come up and use it?
- Yes. The targets are large, and two children can work on the board at the same time.
- Can it show percentages?
- Yes. Tap % and the shaded part is written as a fraction over a hundred, in its lowest terms, as a percentage and as a decimal. Shade half the grid and the board reads 50/100, a half, 50% and 0.5 together.
- Why does % grey out on the 120 grid?
- Because a percentage is out of a hundred. That grid has 120 squares in it, so forty-seven of them is not forty-seven per cent, and the readings would be teaching the wrong thing.
- Can I clear just one colour?
- Tapping a step button again clears that pattern. Undo steps back through individual changes, and Clear removes all the shading.