Worked example · Maths · Year 8
DCF: Data and computational thinking → Data and information literacy
A completed Year 8 budget, with every figure worked out so you can mark the class without doing the arithmetic yourself. Show it in the last ten minutes, or use it to check one table over a pupil's shoulder. Every number below follows from the cost list on the worksheet.
| Row | A — Item | B — Unit cost | C — Qty | D — Line total |
|---|---|---|---|---|
| 2 | Coach hire, 49-seat, school to Cardiff Bay and return | £395.00 | 1 | £395.00 |
| 3 | Techniquest pupil admission | £8.50 | 30 | £255.00 |
| 4 | Techniquest adult admission (free at 1 adult to 10 pupils) | £0.00 | 3 | £0.00 |
| 5 | Science Theatre show supplement, per pupil | £2.00 | 30 | £60.00 |
| 6 | Packed lunch from the school kitchen | £2.85 | 12 | £34.20 |
| 7 | Coach parking, Cardiff Bay | £8.00 | 1 | £8.00 |
| 8 | Hi-vis tabards, pack of 10 | £11.99 | 3 | £35.97 |
| 9 | Workshop: Forces and Motion (whole class) | £45.00 | 1 | £45.00 |
| 10 | First aid kit refill | £6.40 | 1 | £6.40 |
| 11 | Photocopying permission slips and risk assessment | £0.06 | 66 | £3.96 |
| 12 | Contingency fund | £20.00 | 1 | £20.00 |
| 13 | GRAND TOTAL | £863.53 |
Data organised into labelled columns, one item per row — first success criterion. Every line total is unit cost times quantity: 8.50 × 30 = 255.00, 2.85 × 12 = 34.20, 11.99 × 3 = 35.97, 0.06 × 66 = 3.96.
| Cell | Formula typed in | What it shows on screen |
|---|---|---|
| D2 | =B2*C2 | £395.00 |
| D3 | =B3*C3 | £255.00 |
| D4 to D12 | =B4*C4 filled down to =B12*C12 | the rest of column D |
| D13 | =SUM(D2:D12) | £863.53 |
| G2 | typed in: 900 | £900.00 (the agreed budget) |
| G3 | =G2-D13 | £36.47 |
| G4 | =ROUND(D13/30,2) | £28.78 |
| G5 | =D2/$D$13 | 45.7% (the coach's share) |
Every total is a formula, and the grand total uses a range rather than eleven separate additions — second and third success criteria. Change the coach price in B2 and D13, G3, G4 and G5 all update on their own.
1. Grand total. £863.53. Adding the column in order gives 395.00, 650.00, 650.00, 710.00, 744.20, 752.20, 788.17, 833.17, 839.57, 843.53, 863.53.
2. Does it fit? Yes. £900.00 − £863.53 = £36.47 left over, which is about 4% of the budget.
3. Biggest share. The coach, at £395.00. That is 395.00 ÷ 863.53 = 0.457…, so 45.7% of the whole trip — more than pupil admission and the show supplement put together (£315.00).
4. Cost per pupil. 863.53 ÷ 30 = 28.7843…, so £28.78 to the nearest penny. Careful: 30 × £28.78 = £863.40, which is 13p short of the real total, so the letter home should ask for £28.79 (30 × 28.79 = £863.70, 17p over) or round up to £29.00.
5. Four pupils drop out. The cost per pupil goes up, to £31.60. The coach, parking, workshop, tabards, first aid kit and contingency do not get cheaper when fewer pupils go — those fixed items plus the lunches come to £548.53. Only admission and the show are per pupil, at £10.50 each. So with 26 pupils the total is 548.53 + (10.50 × 26) = £821.53, and 821.53 ÷ 26 = £31.60. Fixed costs shared between fewer people always cost each person more.
Reads figures back out of the sheet to answer real questions, including a per-pupil cost and a rounding check — fourth success criterion.
The trip fits the budget. My spreadsheet gives a grand total of £863.53 against the £900.00 agreed, leaving £36.47 unspent, so I recommend going ahead. The one change I would make is the coach: at £395.00 it is 45.7% of the entire cost, and we are only using 33 of its 49 seats. If Year 8 travelled with another class and split the hire, the cost per pupil would fall well below £28.78. I would also ask families for £29.00 rather than £28.78, because 30 × £28.78 only raises £863.40 and leaves us 13p short; £29.00 raises £870.00 and the £6.47 surplus can go into the contingency line.
A conclusion drawn from the pupil's own figures, with the numbers quoted to support it — fifth success criterion.