Take three hands-up answers, not open call-outs. Write each suggestion on the board with the euro amount the pupil names beside it.

Don't correct the totals yet. If two pupils' amounts already add past €100, note it lightly ('we'll see if that all fits') and move on. The tension between wants and the fixed cap is what the whole lesson turns on.

For the €100 party, point at the running total climbing to €100 and the bar landing exactly full — nothing left, nothing over. Ask what would happen if we gave prizes €30 instead.

For the €200 trip, note the bus swallows more than half; the point is that a fixed total forces choices.

The €50 one is the make-or-break: the bar goes red and the total reads €55. Hold out for a pupil to name the fix (take €5 off somewhere) before you say it. That naming is the re-balancing idea landing.

Talk this one through together — pupils take turns at the board and the class agrees or corrects out loud.

Take food first, then drinks, then decorations, then prizes. After each allocation ask the class to read the remaining figure off the readout before the next pupil comes up.

Steer the class toward a deliberate over-shoot on the fourth category so the re-balancing moment happens live: if food, drinks and decorations already total €95, a pupil giving prizes €30 tips it to €125. Don't rush past the red bar — ask which category could give back €5. Revoice a strong answer: so we take five off decorations and the total drops back to exactly €120.

This is the practice round — pupils take turns at the board, check each answer, and the class confirms before moving on. Keep the board work brisk rather than over-explaining.

The non-zero rule is what forces real trade-offs: a pupil can't dump the whole cap on one category. On the €200 trip, watch for the bus eating most of the total and only small amounts left for lunch and entry.

The last challenge is the stretch: the €300 sports day has five categories, so the running total has to be tracked across one more allocation than before and there are more ways to overshoot. There is more than one right answer — accept any allocation that hits €300 with all five non-zero. Ask a pupil who finishes early to explain why their split works before the next pupil comes up.