Year 6 Maths reasoning (SATs): Miles, kilometres and approximate imperial units
Part of the Year 6 Maths reasoning (SATs) measures in context chapter. Chapter overview · whole chapter on one page
Miles, kilometres and approximate imperial units
Rule
Approximate conversions: 1 mile is about 1.6 km. 1 kg is about 2.2 pounds (lb). 1 inch is about 2.5 cm. 1 litre is about 1.75 pints.
These are estimates, so the answer is about a number. Multiply by the rule, then round.
Key ideas
- 5 miles is about 8 km, so 10 miles is about 16 km.
- An approximate conversion gives an answer with about in front.
- Round to a sensible number of whole units.
Method. Multiply by the approximate conversion factor, then round.
- Use the approximate rule: 1 mile is about 1.6 km. The rule is only an estimate, so the answer is about this amount.5 miles x 1.6 = 8.00
- Round to the nearest whole number. Round to the nearest whole number for a sensible answer.about 8 km
- Write the answer. about 8 km
Check. 5 x 1.6 is about 8. ✓
Watch out. Imperial and metric conversions are approximate. Write about in your answer.
Method. Multiply by the approximate conversion factor, then round.
- Use the approximate rule: 1 kg is about 2.2 pounds. The rule is only an estimate, so the answer is about this amount.60 kg x 2.2 = 132.00
- Round to the nearest whole number. Round to the nearest whole number for a sensible answer.about 132 pounds
- Write the answer. about 132 pounds
Check. 60 x 2.2 is about 132. ✓
Watch out. Imperial and metric conversions are approximate. Write about in your answer.
Method. Multiply by the approximate conversion factor, then round.
- Use the approximate rule: 1 inch is about 2.5 cm. The rule is only an estimate, so the answer is about this amount.20 inches x 2.5 = 50.00
- Round to the nearest whole number. Round to the nearest whole number for a sensible answer.about 50 cm
- Write the answer. about 50 cm
Check. 20 x 2.5 is about 50. ✓
Watch out. Imperial and metric conversions are approximate. Write about in your answer.
Watch out
Watch out. A mile is longer than a kilometre. 10 miles is about 16 km, not 10 km.
Exam tip
Practice guide. Use 5 miles = 8 km as a check when you are not sure of the rule.
Exercise 4C Practice: miles, kilometres and imperial units
Non-calculatorMethod. Multiply by the approximate conversion factor, then round.
- Use the approximate rule: 1 mile is about 1.6 km. The rule is only an estimate, so the answer is about this amount.10 miles x 1.6 = 16.00
- Round to the nearest whole number. Round to the nearest whole number for a sensible answer.about 16 km
- Write the answer. about 16 km
Check. 10 x 1.6 is about 16. ✓
Watch out. Imperial and metric conversions are approximate. Write about in your answer.
Method. Multiply by the approximate conversion factor, then round.
- Use the approximate rule: 1 mile is about 1.6 km. The rule is only an estimate, so the answer is about this amount.26 miles x 1.6 = 41.60
- Round to the nearest whole number. Round to the nearest whole number for a sensible answer.about 42 km
- Write the answer. about 42 km
Check. 26 x 1.6 is about 42. ✓
Watch out. Imperial and metric conversions are approximate. Write about in your answer.
Method. Multiply by the approximate conversion factor, then round.
- Use the approximate rule: 1 kg is about 2.2 pounds. The rule is only an estimate, so the answer is about this amount.4 kg x 2.2 = 8.80
- Round to the nearest whole number. Round to the nearest whole number for a sensible answer.about 9 pounds
- Write the answer. about 9 pounds
Check. 4 x 2.2 is about 9. ✓
Watch out. Imperial and metric conversions are approximate. Write about in your answer.
Method. Multiply by the approximate conversion factor, then round.
- Use the approximate rule: 1 litre is about 1.75 pints. The rule is only an estimate, so the answer is about this amount.3 litres x 1.75 = 5.25
- Round to the nearest whole number. Round to the nearest whole number for a sensible answer.about 5 pints
- Write the answer. about 5 pints
Check. 3 x 1.75 is about 5. ✓
Watch out. Imperial and metric conversions are approximate. Write about in your answer.
Method. Multiply by the approximate conversion factor, then round.
- Use the approximate rule: 1 inch is about 2.5 cm. The rule is only an estimate, so the answer is about this amount.2 inches x 2.5 = 5.00
- Round to the nearest whole number. Round to the nearest whole number for a sensible answer.about 5 cm
- Write the answer. about 5 cm
Check. 2 x 2.5 is about 5. ✓
Watch out. Imperial and metric conversions are approximate. Write about in your answer.
Method. Test each choice against the question.
- Read what the question asks. Decide what the answer must do or show.
- Test the choice. 10 km is about 10 / 1.6 = 6 miles, because a mile is longer than a kilometre.about 6 miles fits
- Reject the other choices. About 16 miles would be 10 miles in km, the wrong way round. About 10 miles is the same number, which is wrong.about 16 miles and about 10 miles do not fit
- Write the answer. about 6 miles
Check. about 6 miles is the one that fits. ✓
Method. Multiply the miles by 1.6.
- Multiply. 20 x 1.6 = 32.32 km
- Write the answer. 32 km
Check. 32 / 1.6 = 20. ✓
Method. Convert one of the distances to the other unit.
- Convert 10 miles. 10 x 1.6 = 16 km.16 km
- Compare. 16 km is more than 10 km.10 miles is longer
- Write the answer. Because 10 miles is about 16 km, which is longer than 10 km.
Check. 16 > 10. ✓
Method. Multiply by 2.2, then round to the nearest whole number.
- Multiply. 3.5 x 2.2 = 7.7.7.7
- Round. 7.7 rounds to 8.8 pounds
- Write the answer. 8 pounds
Check. 8 / 2.2 is about 3.6, close to 3.5. ✓
Method. Find the total miles, then convert.
- Total miles. 15 + 8 = 23 miles.23
- Convert. 23 x 1.6 = 36.8, which rounds to 37 km.37 km
- Write the answer. 37 km
Check. 23 x 1.6 = 36.8. ✓
Method. Test each option.
- Check each option. Test each one against the rule or the calculation.
- Tick the true ones. 5 miles is about 8 km, and 2 inches is about 5 cm (1 inch is about 2.5 cm).5 miles is about 8 km, 2 inches is about 5 cm
- Leave the others unticked. These do not match.1 kg is about 10 pounds, 1 litre is about 5 pints are not ticked
- Write the answer. 5 miles is about 8 km, 2 inches is about 5 cm
Check. Each ticked option is true. ✓
Watch out. 1 kg is about 2.2 pounds, not 10. 1 litre is about 1.75 pints, not 5.
Method. Use 8 km = 5 miles to scale.
- Find 1 km. 80 / 8 = 10, so 80 km = 10 lots of 8 km.10
- Multiply. 10 x 5 = 50 miles.50 miles
- Write the answer. 50 miles
Check. 8 km = 5 miles, so 80 km = 50 miles. ✓