Mult-e-Maths



Converting Units of Measure 6MEA2

National curriculum objective

Pupils should be taught to:

• use, read, write and convert between standard units, converting measurements of length, mass, volume and time from a smaller unit of measure to a larger unit, and vice versa, using decimal notation to up to three decimal places.

Prior knowledge and skills

• Understand the prefixes kilo-, centi-, milli-.

• Understand and use place value to multiply and divide by 10, 100, 1000.

• Know basic units and their uses (length – metre; mass –gram; volume – litre; time – hours, minutes, seconds).

Vocabulary

metre, litre, gram, kilo-, centi-, milli-

Resources

• small whiteboards and pens

• metre stick or metre rule

• Resource sheets 1 and 2

Oral and mental starter

Pupils might find it useful to use their small whiteboards for some of the working out in this lesson.

Whole class

Hold up a metre stick. Ask pupils how long it is.

Q How long is this? (Answers might vary: 1 metre, 100 cm, 1000 mm)

If pupils only say 1 m and do not say 100 cm or 1000 mm, ask:

Q What other lengths are equal to 1 metre? (100 cm, 1000 mm)

You might need to discuss with pupils the meanings of the prefixes kilo- (1000), centi- (1/100 or one hundredth), and milli- (1/1000 or one thousandth).

Q How many metres sticks would you need in order to make 1 km? (1000)

Main teaching activity

Whole class

(Screen 1: Activity 1, Question 1)

Q How can you convert between metres and centimetres? (Multiply by 100 to go from metres to centimetres; divide by 100 to go from centimetres to metres.)

The diagram on screen 1 shows these conversions as a diagram with arrows. Discuss with pupils that the chart is similar to a place value chart. Kilo- is in the thousands place; the base unit, such as metre or gram, is in the ones place; centi- in the hundredths place; and milli- in the thousandths place.

Drag the yellow panels to the bin and reveal conversions between a larger range of measures: for example, km to mm.

Pupils practise using the chart on the board to convert between these measures:

140 cm to mm (1400 mm)

1.3 km to m (1300 m)

6.5 m to mm (6500 mm)

32 mm to cm (3.2 cm)

49 cm to m (0.49 m)

3750 cm to m (37.5 m)

Explain to pupils that this chart works for other units that use the prefixes kilo-, centi- and milli-, such as litres and grams.

Groups or Pairs

Pupils work in groups or pairs to complete the questions on the Resource sheet 1. You might need to explain to pupils that when moving to the right on the conversion chart (for example, kilometres to centimetres), they use multiplication, and when they move to the left (for example, milligrams to grams) they use division. The chart on the Resource Sheet only shows multiplication.

After pupils have completed the questions, discuss solutions and strategies with pupils. Resolve any queries.

Whole class

(Screen 2: Activity 2, Question 1)

Pupils practise converting between units of time. Remind pupils that to convert between hours, minutes, and seconds you need to multiplying and dividing by 60.

Q How many minutes are in 2 hours? (120; 2 × 60)

How many seconds are in 1 hour? (3600; 1 × 60 × 60)

Ask pupils to practise converting between these measures, using the chart if necessary:

3 hours to minutes (180 minutes)

150 minutes to hours (2.5 hours)

1200 seconds to minutes (20 minutes)

96 000 minutes to hours (1600 hours)

24 hours to seconds (86 400 seconds)

Groups or Pairs

Pupils to work in groups or pairs to complete Resource sheet 2. After they have completed the questions, discuss solutions and strategies. Resolve any queries.

Other tasks

You could ask pupils to:

• research the prefixes to go in the blank columns of the chart on Resource sheet 1. For example, what prefix means tenths?

Review

(Screen 3: Activity 3, Question 1)

Ask pupils to match the three prefixes with their meanings (Kilo- thousands, centi- hundredths, and milli- thousandth). Invite a pupil to drag one matching pair into each orange panel.

(Screens 4: Activity 4, Question 1)

Ask pupils to sort the measurements into the correct order from longest to shortest.

Q Which measurement is the longest? (8 km)

Drag this to the far left side of the screen, and continue.

Pupils can use their small whiteboards to help if necessary.

Correct order (longest to shortest):

8 km; 1 800 000 mm; 0.235 km; 210 m; 3 m;

0.512 m; 45 cm; 240 mm; 60 mm; 5 cm; 42 mm

Key ideas and assessment

Converting between standard units of length, mass and volume involves multiplying or dividing by a power of 10. The prefixes kilo-, centi- and milli- can be related to a place value chart: kilo- is in the thousands place; the base unit, such as metre or gram, is in the ones place; centi- in the hundredths place; and milli- in the thousandths place. To convert between different units of time, you multiply or divide by 60.

Can pupils:

• convert between larger and smaller units of measure?

• convert between larger and smaller units of measure using decimal notation up to three decimal places?

• use place value to convert between units of measure involving kilo-, centi-, milli-?

Solutions

Resource sheet 1

1. 470 2. 3800 3. 1200  4. 6700

5. 5850 6. 79.9 7. 5 900 000 8. 0.42

9. 0.0095 10. 12.5 11. 69.7 12. 45 500

Resource sheet 2

1. 120 2. 45 3. 6

4. 150 5. 0.03 6. 5400

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