C1.16 Money
- Syllabus
- 0580–2028–2029
- Topic
- C1.16
- Level
- Core
Learning objectives
Calculate totals, bills and change
Money calculations combine quantities, unit prices and payment rules. Keep every amount in one currency and one unit, model the whole bill, then format the final amount appropriately.
| Money job | Calculation structure |
|---|---|
| Cost of several items | quantity × unit price |
| Total bill | add every item or charge once |
| Change | amount paid − total bill |
| Fixed fee plus usage | fixed fee + number of additional units × extra-unit price |
| Maximum whole items | divide budget by unit price, then take the whole-number part |
With 20 dollars and pineapples costing 1.45 dollars each, 20÷1.45=13.79…, so at most 13 can be bought. Their cost is 13×1.45=18.85 dollars, leaving 20−18.85=1.15 dollars change.
Convert cents and dollars before combining them: 47 cents is 0.47 dollars, while 5 dollars is 500 cents. For mass or volume prices, also match the quantity unit; 125 ml is 0.125 litres before multiplying by a price per litre.
Read special pricing literally. “Buy 3 for the price of 2” means every complete group of 3 costs 2 unit prices. “First hour 15.50 dollars, each additional hour 7.25 dollars” means the first hour is not charged again at 7.25 dollars.
Round a final money answer to the smallest stated currency unit, normally two decimal places for dollars. Do not round a unit price or intermediate total early, and never round a maximum item count upward beyond the available budget.
Convert currencies using the stated exchange rate
An exchange rate is a unit rate. Read its direction before calculating: if 1 unit of currency A equals r units of currency B, then r converts one A into B.
1 A=r B
| Conversion | Operation | Unit check |
|---|---|---|
| A to B | multiply by r | A × B/A = B |
| B to A | divide by r | B ÷ B/A = A |
If 1 rupee = 0.016 dollars, a 20-dollar ticket costs 20÷0.016=1250 rupees. Division is required because the given rate tells how many dollars one rupee is worth, not how many rupees one dollar buys.
For two currencies with a common bridge, convert in two labelled stages. If 1 dollar = 0.615 euros and 1 krona = 0.087 euros, then 2000 dollars becomes 2000×0.615=1230 euros, then 1230÷0.087=14137.93… krona, or 14 138 krona to the nearest krona.
To compare prices in different currencies, convert both prices into the same currency first, subtract to find the difference, and round only the final requested amount.
Do not choose multiply or divide from whether the number should become larger. Currency values vary; let the written rate and units determine the operation. Keep full precision until the final money rounding.