Interactive hundred square for the whiteboard

What the interactive hundred square does on screen

One ten by ten grid fills the board with its controls in a row along the top. Every one of them is a single press, so you can change the grid while you are still talking.

• Colouring in. Tap a square and it turns yellow, tap it again to clear it. The round chips in the black bar swap the yellow for coral, blue, green or violet, so two patterns can be marked in two colours at once. Clear wipes the colouring and leaves any lit-up table alone.
• Two tables at once. Count in sets the first pattern and the box beside it a second, each offering Odd, Even and the tables from 2 to 12. The squares light one after another across the grid: the first table mint green, the second pink, and any number in both lilac.
• Which numbers. Range gives 1 to 100, 0 to 99, 1 to 120 and 101 to 200, and Start at begins the grid on any number you type. +100 and −100 move it a hundred at a time. On a 0 to 99 grid every number in a row shares a tens digit, and Flip turns the whole grid over so 1 sits at the bottom left, the way some schools teach it.
• Blanking numbers. Hide blanks the marker's row, its column, its diagonal, a random twelve (Splat) or all hundred at once. Tap a blank to bring that number back, or press Reveal for the lot. The ? chip turns a tap into a blank, so you can choose the gaps yourself.
• The marker, and counting on. A red outline sits on one square. Drag it anywhere, or walk it with −10, −1, +1 and +10, and every hop it makes is ringed in green so the class can see the route it took. Count on carries it from wherever it stands in whatever step you type, one square at a time with Next or on its own with Play.
• The number in words. Under the grid the marker's number is written out, forty-seven, one hundred and forty-seven. Words turns it off when you want the class to say it first.
• Print. One A4 landscape picture of the grid as it looks, colours, blanks, marker, trail and all.

How to use it in a lesson

Set the grid up before the class is looking at it. Watching the colour appear all at once hides the thinking; asking what the next row will look like does not.

1. Pick the numbers first. 1 to 100 for counting work, 0 to 99 the moment the lesson is about tens and ones, 1 to 120 when the class is crossing a hundred.
2. Light one table and read it down together before you say anything about the pattern. What do the coloured numbers all end in?
3. Add the second table and predict. Which squares will go lilac? Take three guesses, then set it and check.
4. Park the marker somewhere awkward, 47 will do, and press +10 four times. Which digit is moving and which is standing still?
5. Press Splat and work the twelve gaps as a class, tapping each to check as you get it.
6. Count on in 3s from 4 with Next, one press per child round the carpet, and stop before the last one to ask where it will land.
7. Step past a hundred, then Print the board if you want the same grid on paper for the ones who need it in front of them.

Ideas by year group

• Year 1. Count along the first three rows together, tapping each square as you say it, then shade every number with a 5 in it.
• Year 2. Count in 2s and 5s together. Which squares are lilac, and what is the next one after 50?
• Year 3. Marker on 37, then +10 three times. The units digit never moves, which is adding ten in one column.
• Year 4. Press Splat, then make the class justify each answer from its row and column rather than counting from 1.
• Year 5. Count in 6s and 8s. The first lilac square is the lowest common multiple, and the gap to the next is the same again.
• Year 6. Light the 9s, then press +100 twice. Does the pattern still work up in the two hundreds, and why does it have to?

The misconceptions it helps with

Adding ten by counting on ten. A child going 47, 48, 49 up to 57 loses count and loses the pattern with it. The marker dropping one square makes it one move, not ten.

Stalling at the end of a row. Plenty of children get to 39 and stop. The marker walking off the end and reappearing at the start of the next row makes the wrap ordinary rather than mysterious.

A number belongs to one table only. Twelve is in the twos, threes, fours and sixes. Two colours and a lilac overlap settle that in seconds, and no list ever has.

Bigger numbers behave differently. Step to 201 to 300 with a table lit and the pattern sits in exactly the same squares.

Frequently asked questions