Addition and Subtraction Strategies for addition and subtraction

Addition and Subtraction Strategies for addition and subtraction Objectives Day 1 Know number facts to 20; Understand the concept of equality and use the sign; Relate addition and subtraction in the context of number facts. Add pairs of 2-digit numbers using a mental strategy. Day 2 Add 1-digit numbers to 2-digit numbers using number facts. Add 1-digit numbers to 3-digit numbers using number facts. Day 3 Subtract 1-digit numbers from 2-digit numbers using number facts. Subtract 1-digit numbers from 3-digit numbers using number facts. hamilton-trust.org.uk 1 Year 3/4

Addition and Subtraction Strategies for addition and subtraction Short Mental Workouts Day 1 Addition facts for numbers 6 to 10. Day 2 Know by heart totals of any pair of 1-digit numbers. Day 3 Complements to multiples of 10. hamilton-trust.org.uk 2 Year 3/4

Addition and Subtraction Strategies for addition and subtraction Short Mental Workout Addition facts for numbers 6 to 10. hamilton-trust.org.uk 3 Year 3/4

hamilton-trust.org.uk 4 Year 3/4

Addition and Subtraction Strategies for addition and subtraction Short Mental Workout Know by heart totals of any pair of 1-digit numbers. hamilton-trust.org.uk 5 Year 3/4

Addition and Subtraction Strategies for addition and subtraction Short Mental Workout Complements to multiples of 10. hamilton-trust.org.uk 6 Year 3/4

Addition and Subtraction Strategies for addition and subtraction Objectives Day 1 Know number facts to 20; Understand the concept of equality and use the sign; Relate addition and subtraction in the context of number facts. Add pairs of 2-digit numbers using a mental strategy. hamilton-trust.org.uk 7 Year 3/4

Day 1: Know number facts to 20; Understand the concept of equality and use the sign; Relate addition and subtraction in the context of number facts; Add pairs of 2-digit numbers using a mental strategy. This picture shows that 8 and 4 cubes are the same amount as 12 cubes. 12 12 44 88 and and 12 12 88 44 12 12 -- 44 88 if we took If What we took away 4 away cubes8 cubes instead? how many would be left? hamilton-trust.org.uk 12 12 -- 88 44 8 Year 3/4

Day 1: Know number facts to 20; Understand the concept of equality and use the sign; Relate addition and subtraction in the context of number facts; Add pairs of 2-digit numbers using a mental strategy. 88 44 12 12 We We can can write also draw 4 number bars to 44 88 12 12 sentences represent for this the cubes picture 12 12 -- 44 88 12 12 -- 88 44 hamilton-trust.org.uk 9 Year 3/4

Day 1: Know number facts to 20; Understand the concept of equality and use the sign; Relate addition and subtraction in the context of number facts; Add pairs of 2-digit numbers using a mental strategy. In pairs, choose one of the number bars Did each set of numbers have 4 and write all of the addition and addition and subtraction facts? subtraction facts for it. Are there any other pairs of numbers that add to 12? hamilton-trust.org.uk 10 Year 3/4

Day 1: Know number facts to 20; Understand the concept of equality and use the sign; Relate addition and subtraction in the context of number facts; Add pairs of 2-digit numbers using a mental strategy. What should I put on the right to make it balance? Let’s put 6 and 4 on the left of the balance and 7 on the right. What will happen? 6 4 7 3? 66 44 77 3?3? The equals sign acts like the middle of a see-saw hamilton-trust.org.uk 11 Year 3/4

Day 1: Know number facts to 20; Understand the concept of equality and use the sign; Relate addition and subtraction in the context of number facts; Add pairs of 2-digit numbers using a mental strategy. What should I put on the left to make it balance? Let’s put 6 on the left on the left of the balance and 9 and 1 on the right 6 4? 9 1 66 4?4? 99 11 hamilton-trust.org.uk 12 Year 3/4

Day 1: Know number facts to 20; Understand the concept of equality and use the sign; Relate addition and subtraction in the context of number facts; Add pairs of 2-digit numbers using a mental strategy. What should I put on the right to make it balance? Let’s put 7 and 6 on the left of the balance and 8 on the right 7 6 8 5? 77 66 88 5?5? hamilton-trust.org.uk 13 Year 3/4

Day 1: Know number facts to 20; Understand the concept of equality and use the sign; Relate addition and subtraction in the context of number facts; Add pairs of 2-digit numbers using a mental strategy. What should I put on the left to make it balance? Let’s put 6 on the left on the left of the balance and 9 and 4 on the right 6 7? 9 4 66 7?7? 99 44 hamilton-trust.org.uk 14 Year 3/4

Day 1: Know number facts to 20; Understand the concept of equality and use the sign; Relate addition and subtraction in the context of number facts; Add pairs of 2-digit numbers using a mental strategy. Talk Talk to to your your partner partner –– what what other other pairs pairs make make 13? 13? We We can can try try them them on on the the balance! balance! How can you be sure you have found them all? hamilton-trust.org.uk 15 Year 3/4

Challenge hamilton-trust.org.uk 16 Year 3/4

Day 1: Add pairs of 2-digit numbers using a mental strategy. 48 80 24 57 Which Which is is the the best best way way to to do do each each of of these these 44 additions? additions? Choose Choose aa pair pair of of numbers numbers to to add. add. hamilton-trust.org.uk 17 Year 3/4

Day 1: Add pairs of 2-digit numbers using a mental strategy. Here are some examples I can add 24 and 48 by partitioning and recombining 48 48 24 24 40 40 20 20 88 44 60 60 12 12 72 72 I can add 48 to 57 by adding 50 then subtracting 2. I can add 80 and 24 by adding 20 to 80 and then 4 more. Any other ideas? hamilton-trust.org.uk 18 Year 3/4

hamilton-trust.org.uk 19 Year 3/4

Addition and Subtraction Strategies for addition and subtraction Objectives Day 2 Add 1-digit numbers to 2-digit numbers using number facts. Add 1-digit numbers to 3-digit numbers using number facts. hamilton-trust.org.uk 20 Year 3/4

Day 2: Add 1-digit numbers to 2-digit numbers using number facts; Add 1-digit numbers to 3-digit numbers using number facts. 15 25 35 Now let’s try 25 3 and 35 3. Let’s use this bead bar to help us find 15 3. Y4s: Y4s: What What is is 105 105 3? 3? 125 125 3? 3? 245 245 3? 3? 845 845 3? 3? Y3s: Y3s: How How will will this this sequence sequence continue? continue? hamilton-trust.org.uk 21 Year 3/4

Day 2: Add 1-digit numbers to 2-digit numbers using number facts; Add 1-digit numbers to 3-digit numbers using number facts. 17 What is 17 7? What do we need to add to 17 to make 20? How much of the 7 is left to add on to 20? What if we want to add 7 to 27? hamilton-trust.org.uk 22 Year 3/4

Day 2: Add 1-digit numbers to 2-digit numbers using number facts; Add 1-digit numbers to 3-digit numbers using number facts. 3 4 37 44 37 7 44 Let’s try 37 7. We can draw the steps on the number line to help What would 47 7 and 57 7 be? What would the jumps look like? hamilton-trust.org.uk 23 Year 3/4

Day 2: Add 1-digit numbers to 2-digit numbers using number facts; Add 1-digit numbers to 3-digit numbers using number facts. 5 2 58 60 65 Y3: Y3: How How can can you you work work out out 58 58 7? 7? Would Would you you 58 7 65 77 the split the same way? We cansplit show thatsame on way? an empty number line. What is 258 7? Y4: Y4: How How can can you you work work out out 258 258 7? 7? hamilton-trust.org.uk 24 Year 3/4

Challenge hamilton-trust.org.uk 25 Year 3/4

Challenge hamilton-trust.org.uk 26 Year 3/4

Addition and Subtraction Strategies for addition and subtraction Objectives Day 3 Subtract 1-digit numbers from 2-digit numbers using number facts. Subtract 1-digit numbers from 3-digit numbers using number facts. hamilton-trust.org.uk 27 Year 3/4

Day 3: Subtract 1-digit numbers from 2-digit numbers using number facts; Subtract 1-digit numbers from 3-digit numbers using number facts. 15 25 35 Let’s use this bead bar to help us find 15 - 2. So what is 25 - 2 and 35 - 2? Y3: Y3: Talk Talk to to your your partner partner –– how how do do you you think think this this sequence sequence will will continue? continue? hamilton-trust.org.uk What number fact helps? Y4: Y4: What What is is 105 105 -- 2? 2? 125 125 -- 2? 2? 465 465 -- 2? 2? 28 Year 3/4

Day 3: Subtract 1-digit numbers from 2-digit numbers using number facts; Subtract 1-digit numbers from 3-digit numbers using number facts. 24 What is 24 - 4? Knowing that we can split the 7 into 4 and 3 makes finding 24 -7 a quick, 2-step strategy: 24 - 4 - 3 24 - 4 is 20. That’s a place value subtraction. What is 24 - 7? How can we split the 7 to help? hamilton-trust.org.uk Then 20 - 3 17. That’s a number fact we know, based on 10 - 3 7. 29 Year 3/4

Day 3: Subtract 1-digit numbers from 2-digit numbers using number facts; Subtract 1-digit numbers from 3-digit numbers using number facts. 3 4 27 34 34 - 7 27. Let’s try 34 - 7. We can draw the steps on the number line to help What would 44 - 7 and 57 - 7 be? What would the jumps look like? hamilton-trust.org.uk 30 Year 3/4

Day 3: Subtract 1-digit numbers from 2-digit numbers using number facts; Subtract 1-digit numbers from 3-digit numbers using number facts. 5 55 2 60 62 Y3: Y3: How How can can you you work work out out 62 62 -- 7? 7? How How would would you you split split the the 7? 7? 62 - 7 55 We can show that on an empty number line. What is work 562 - 7? Y4: Y4: How How can can you you work out out 562 562 -- 7? 7? hamilton-trust.org.uk 31 Year 3/4

Challenge hamilton-trust.org.uk 32 Year 3/4

Challenge hamilton-trust.org.uk 33 Year 3/4

Addition and Subtraction Strategies for addition and subtraction Well Done! You’ve completed this unit. Objectives Day 1 Know number facts to 20; Understand the concept of equality and use the sign; Relate addition and subtraction in the context of number facts. Add pairs of 2-digit numbers using a mental strategy. Day 2 Add 1-digit numbers to 2-digit numbers using number facts. Add 1-digit numbers to 3-digit numbers using number facts. Day 3 Subtract 1-digit numbers from 2-digit numbers using number facts. Subtract 1-digit numbers from 3-digit numbers using number facts. hamilton-trust.org.uk 34 Year 3/4

Problem Problem solving solving and and reasoning reasoning questions questions Year Year 33 Write Write 44 number number sentences sentences to to relate relate these these three three numbers: numbers: 13, 13, 19 19 and and 6. 6. We We know know 13 13 77 20. 20. So, So, what what isis 130 130 70? 70? We We know know 11 11 99 20. 20. So, So, what what isis 110 110 90? 90? Write Write an an addition addition with with an an answer answer of of 20. 20. Write Write aa related related addition addition with with an an answer answer of of 200. 200. Repeat Repeat for for two two more more pairs pairs of of numbers numbers that that total total 20, 20, then then 200. 200. hamilton-trust.org.uk 35 Year 3/4

Problem Problem solving solving and and reasoning reasoning answers answers Year Year 33 Write Write 44 number number sentences sentences to to relate relate these these three three numbers: numbers: 13, 13, 19 19 and and 6. 6. 13 13 66 19, 19, 66 13 13 19, 19, 19 19 -- 13 13 6, 6, 19 19 -- 66 13 13 We We know know 13 13 77 20. 20. So, So, what what isis 130 130 70? 70? 200 200 We We know know 11 11 99 20. 20. So, So, what what isis 110 110 90? 90? 200 200 Write Write an an addition addition with with an an answer answer of of 20. 20. Write Write aa related related addition addition with with an an answer answer of of 200. 200. Repeat Repeat for for two two more more pairs pairs of of numbers numbers that that total total 20, 20, then then 200. 200. e.g. e.g. 10 10 10 10 20, 20, 100 100 100 100 200 200 15 15 55 20, 20, 150 150 50 50 200. 200. Do Do children children make make the the connection connection between between the the initial initial number number fact fact to to 20 20 and and the the subsequent subsequent questions? questions? hamilton-trust.org.uk 36 Year 3/4

Problem Problem solving solving and and reasoning reasoning questions questions Year Year 44 Write Write 44 number number sentences sentences to to relate relate these these three three numbers: numbers: 240, 240, 390 390 and and 150. 150. Use Use aa mental mental method method to to find: find: 150 150 50 50 35 35 65 65 192 192 66 66 66 29 29 153 153 39 39 200 200 –– 52 52 240 240 550 550 73 73 –– 25 25 630 630 –– 150 150 hamilton-trust.org.uk 37 Year 3/4

Problem Problem solving solving and and reasoning reasoning answers answers Year Year 44 Write Write 44 number number sentences sentences to to relate relate these these three three numbers: numbers: 240, 240, 390 390 and and 150. 150. 240 240 150 150 390, 390, 150 150 240 240 390, 390, 390 390 -- 150 150 240, 240, 390 390 -- 240 240 150 150 Use Use aa mental mental method method to to find: find: 150 35 150 50 50 200 200 35 65 65 100 100 192 66 192 66 198 198 66 29 29 95 95 153 153 39 39 192 192 240 240 550 550 790 790 200 200 –– 52 52 148 148 73 73 –– 25 25 48 48 630 630 –– 150 150 480 480 Check Check children’s children’s strategiesstrategies- are are they they best best suited suited for for the the numbers, numbers, for for example example adding adding and and adjusting adjusting (66 (66 29), 29), using using complements complements (35 (35 65), 65), bridging bridging (73 (73 –– 25). 25). Can Can they they explain explain their their choices? choices? hamilton-trust.org.uk 38 Year 3/4