4.1 Changing units
You will sometimes need to change between millilitres and litres. There are 1,000 millilitres in a litre.
Take a look at this section of the metric conversion chart to refer to when you are carrying out the activity below.
Example: Hospital catering
The hospital catering staff have an order for 40 vegetarian meals. The recipe they are using calls for 600 ml of milk to make enough for four people.
How many litres of milk will they need to make ten times as much?
First you need to multiply the amount in millilitres by 10:
- 600 × 10 = 6,000 ml
However, the question asks for an amount in litres, not millilitres. To convert from millilitres to litres, you need to divide the figure in millilitres by 1,000. So the amount of milk you need in litres is:
- 6,000 ÷ 1,000 = 6 litres
Now try the following activity using the conversion diagram above to help you answer the questions. Remember to check your answers once you have completed the questions.
Activity 10: Converting between millilitres, centilitres and litres
- A nurse has to order enough soup for 100 patients on a ward. Each patient will eat 400 ml of soup. How many litres of soup must the nurse order?
- Twenty people working in a craft workshop have to share the last two-litre bottle of glue. How many millilitres of glue can each person use? What would this be in centilitres?
- First you need to work out how much soup you will need in millilitres:
- 100 × 400 = 40,000 ml
To convert from millilitres to litres, you need to divide the figure in millilitres by 1,000. So the amount of milk you need in litres is:
- 40,000 ÷ 1,000 = 40 litres
- First you need to work out how many millilitres are in 2 litres of glue:
- 2 × 1,000 = 2,000 ml
This amount is then divided between the twenty people working in the shop:
- 2,000 ÷ 20 = 100 ml each
To convert this into centilitres, you would divide this answer by 10:
- 100 ÷ 10 = 10 cl each