Time conversion
2.5 hours is 150 minutes.
1 hour is 60 minutes.
Year 6
Use, read, write and convert between standard units, converting measurements of length, mass, volume and time, and understand approximate equivalences between miles and kilometres
Use standard units confidently and understand the approximate link between miles and kilometres.
Lesson overview
Measurement
Some conversions are exact, such as minutes to seconds or kilograms to grams. Miles and kilometres are not exact in everyday mental calculation, so we often use the known approximation of 5 miles being about 8 kilometres.
Miles and kilometres
5 miles is about 8 kilometres.
This is an approximate equivalence used for estimation.
Worked example
About how many kilometres is 15 miles?
| Miles | Kilometres |
|---|---|
| 5 | 8 |
| 15 | 24 |
- Use the known fact that 5 miles is about 8 km.
- 15 miles is 3 lots of 5 miles.
- So multiply 8 km by 3.
- 15 miles is about 24 km.
Try it
Decide whether the conversion is exact or an everyday approximation.
Question 1
2.5 hours =
Question 2
5 miles is about:
Question 3
15 miles is about:
| 5 miles | 15 miles |
|---|---|
| 8 km | 24 km |
Question 4
3 kg =
Question 5
90 minutes =
Common mistakes
Watch for these when working through the lesson.
- Treating miles to kilometres as an exact conversion in mental work.
- Using the wrong unit relationship for time or mass.
- Forgetting to scale the known conversion properly.
Related topics
These ideas fit closely with this lesson.
- Solve problems involving the calculation and conversion of units of measure.
- Use decimal place value accurately.