Best buys
- Compare the price of the same amount, such as the price per 100 g, or how much you get for £1. The lower price per unit is the better buy.
- 500 g for £2.40 is 48p per 100 g. 750 g for £3.30 is 44p per 100 g, so the 750 g pack is better value.
- Make sure both amounts are in the same units before you compare.
Exchange rates
- To change pounds into another currency, multiply by the rate. To change back, divide.
- If £1 = €1.15, then £200 = €230, and €69 = £60.
Metric conversions
- Length: 10 mm = 1 cm, 100 cm = 1 m, 1000 m = 1 km. Mass: 1000 g = 1 kg, 1000 kg = 1 tonne. Capacity: 1000 ml = 1 litre, and 1 cm³ = 1 ml.
- Area and volume use the square and cube of the length factor: 1 m² = 100 × 100 = 10 000 cm², and 1 m³ = 1 000 000 cm³.
Time and imperial units
- Time is not decimal: 1.25 hours = 1 hour 15 minutes.
- Imperial conversions are given in the exam, such as 5 miles ≈ 8 km and 1 kg ≈ 2.2 pounds (lb).
Key terms
- Best buy
- The option that gives the most for your money.
- Unit price
- The cost of one unit, such as the price per 100 g.
- Exchange rate
- How much of one currency you get for one unit of another.
- Metric units
- Units based on 10, 100 and 1000, such as metres and grams.
- Imperial units
- Older units such as miles, pounds (lb) and pints.
- Conversion factor
- The number you multiply or divide by to change units.