About this game

A glass jar sits on the teacher's table. Acorns, shells or beetles drop into it, and the lid goes on. Everyone writes a guess on their mini whiteboard.

Then the jar tips over. Each item lands in a row of ten, and the number on the screen goes up by ten as each row fills: 10, 20, 30. The last few are counted one at a time. Hold up the whiteboards and see who was closest.

Every class gets the same jar on the same day, and a new one after midnight.

How it works

1. Pick the size of the numbers: up to 50, 200 or 500.
2. Press Fill the jar. Set a thinking timer if you want one.
3. Press Tip it out when everyone has written a guess.
4. If you turn it on, the pour stops after the first 10 so the class can look at the jar again and change their guess.
5. You can also put a row of 10 beside the jar for the class to compare with.

Good for

• Seeing what 10 and 100 of something look like
• Practising counting in tens
• A five-minute warm-up at the start of a maths lesson