Year 5, Unit 3, Week 3, Lesson 2 Using approximate equivalences between metric and imperial units of mass National Curriculum attainment target Lesson objective • Understand and use approximate equivalences • Know and use approximate equivalences between metric units of between metric units and common imperial units mass (kilograms and grams) and common imperial units (pounds) such as pounds

Prerequisites for learning Success criteria Pupils need to: Pupils can: • read and interpret scales • use the equivalence of 1 kg ≈ 2·2 lb to convert metric units Vocabulary to imperial units and vice versa metric, kilogram (kg), gram (g), imperial, pound (lb), symbol, approximately equal to (≈)

Getting Started • Choose an activity from Measurement (mass).

Te ach Year 5, Unit 3, Week 3 Resources jar of jam labelled 454 g (per class)

• Ask: Who can tell me the names we give to the metric units of mass that we use today? (kilogram and gram) • Ask: Does anyone know the names of some of the units of mass which were in use in your grandparents’ day? (ounce, pound, ton) • Say: The units of mass that our grandparents used are called imperial units. • Tell the children that the imperial units, ounces, pounds and tons are still used in some parts of the world, for example, in the United States of America. • Write on the board: pound (lb) • Say: In the imperial system for mass the pound is written as lb. • Say: You are on holiday in America. You want to buy some sweets from a jar, or since you are in America, candy. Ask: What do you ask for in the candy store? What do you need to know? (how the two systems are related) • Write on the board: 1 kg ≈ 2 lb • Say: Let’s begin by using the relationship one kilogram is approximately equal to two pounds. The wavy equals sign tells us that the two measures are not exactly equal but are near enough. 1 • Display: Slide 1 showing the conversion table for pounds and kilograms using 2 lb ≈ 1 kg. • Point to the table and say: One pound is about 500 grams or half a kilogram. • Ask: How many grams are approximately equal to half/quarter of one pound? (250 g/125 g) • Ask: How many grams are approximately equal to three quarters of one pound? (375 g) How did you fi nd the answer? • Say: There is a more accurate relationship between the kilogram and the pound. 2 • Display: Slide 2 showing the table using the conversion 1 kg ≈ 2·2 lb.

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1000g • Say: Tell your partner what the missing values in the table are. 2 lb 900g • Take feedback and complete the table for the missing values. 3 800g 1 4 lb 3 • Display: Slide 3 showing the conversion scale from 0–1000 g.

1 700g 1 2 lb • Ask a child to read the mass label on the jar of jam. (454 g) Point to 454 g on the scale. 600g 1 • Ask: What can you tell me about the mass of the jar of jam? Take feedback and establish that 1 4 lb 500g 1 lb is not exactly equal to 500 g. 1 lb 454g 400g • Point to the scale and ask: How many grams to the nearest 10 grams are approximately 3 1 4 lb equivalent to 2 lb? (230 g) 300g 3 1 • Say: Tell your partner the imperial mass that is approximately equivalent to 800 g. (14 lb) 2 lb 200g 1 • Repeat with further examples which give the children practice in converting multiples of 4 lb to 1 4 lb 100g grams and vice versa. 0lb 0g • Say: A quick way to link imperial and metric masses is to use the fact that 1 lb is about 500 g.

Individualised Learning Pupil Book 5A: – Page 70: Using metric and imperial units (1) Refer to Activity 2 from the Progress Guide 5: – Support, Year 5, Unit 3, Week 3, Lesson 2: Learning activities on page 168. Metric and imperial card game Resources: scissors (per child) – Extension, Year 5, Unit 3, Week 3, Lesson 2: Honeycomb masses Resources: 4 coloured pencils (per child)

Plenary • Ask: Who can remember the quick way to link imperial and metric masses? (1 lb is about 500 g) • Ask: Using this approximation, how many grams are roughly equal to 4 lb? (2000 g) How many kilograms are roughly equal to 4 lb? (2 kg) …to 10 lb? (5 kg) …to 50 lb? (25 kg) • Say: Tell your partner a quick way to convert kilograms to pounds. (halve the number of kilograms) 3 • Display: Slide 3 showing the conversion scale. • Say: This scale shows a more accurate conversion of pounds to grams. 1 • Ask: What is 12 lb rounded to the nearest 100 g? (700 g) Rounded to the nearest 10 g? (680 g) • Say: A bag of four onions has a mass of 800 g. • Say: Using the conversion scale, tell your partner Homework Guide 5 how to fi nd the mass of one onion to the Year 5, Unit 3, Week 3, Lesson 2: 1 nearest 4 lb. Take feedback and ask several Grocery masses children to explain how they found the answer.

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