Imagine you have exactly €5 to spend at the class tuck shop. A lunch roll costs €3.50, a drink costs €1.50, and a bag of fruit costs €0.90. Could you buy all three? Which two would you pick if you wanted a treat and some money left over?

Watch the budget on the board. The cap at the top is the most we are allowed to spend. As each item goes in, the running total climbs and the amount left goes down. Keep your eye on the bar: when it fills to the very top, the €5 is all used up. Watch closely when a pair of prices would push us over the cap.

Let's build shopping lists together, staying at or under €5. Here are the tuck-shop prices:

• Drink €1.50
• Snack bar €2.20
• Fruit €0.90
• Biscuits €0.80
• Lunch roll €3.50

We will work through these one at a time:

1. Drink and fruit. Does it fit?
2. Snack bar and biscuits. How much is left?
3. Drink and snack bar. How much is left?
4. Add a snack bar to the drink and fruit list. Predict whether it stays under €5 before we check.

Now the tuck shop gets busier. Instead of one list, you are working out what a group of friends spends between them, and what change they get back.

For each round, set how much each friend spends so the total is exactly the amount asked for, then press Check. There is more than one right way to split a total between friends, so any amounts that add up will pass. The last two rounds are about the change, and the change has only one right answer.