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

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 = 4 + 8 and 12 = 8 + 4 12 - 4 = 8 if we took 4 away If What we took away cubes 8 cubes instead? how many would be left? © hamilton-trust. org. uk 12 - 8 = 4 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. 8 + 4 = 12 We 4 number We can write also draw bars to 4 + 8 = 12 sentences for this picture… represent the cubes… 12 - 4 = 8 12 - 8 = 4 © 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 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. Let’s put 6 and 4 on the left of the balance and 7 on the right. What will happen? What should I put on the right to make it balance? 6+4 7 + 3? 6 + 4 = 7 + 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. Let’s put 6 on the left of the balance and 9 and 1 on the right… What should I put on the left to make it balance? 6 + 4? 9+1 6 + 4? = 9 + 1 © 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? 7 + 6 = 8 + 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. Let’s put 6 on the left of the balance and 9 and 4 on the right… What should I put on the left to make it balance? 6 + 7? 9+4 6 + 7? = 9 + 4 © 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 to your partner – what other pairs make 13? We can try them on the 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 is the best way to do each of these 4 additions? Choose a pair of numbers to 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 + 24 = 40 + 20 + 8 + 4 = 60 + 12 = 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

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. Y 4 s: What is 105 + 3? 125 + 3? 245 + 3? 845 + 3? Y 3 s: How will this sequence 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 Y 3: How can you work out 58 + 7? Would you split 7 the same way? We can show that on an empty number line. 58 + 7 = 65 What is 258 + 7? Y 4: How can you work out 258 + 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? Y 3: Talk to your partner – how do you think this sequence will continue? © hamilton-trust. org. uk What number fact helps? Y 4: What is 105 - 2? 125 - 2? 465 - 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 - 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 27 4 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 Y 3: How can you work out 62 - 7? How would you split the 7? 62 - 7 = 55 We can show that on an empty number line. What is work 562 - 7? Y 4: How can you out 562 - 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 solving and reasoning questions Year 3 Write 4 number sentences to relate these three numbers: 13, 19 and 6. We know 13 + 7 = 20. So, what is 130 + 70? We know 11 + 9 = 20. So, what is 110 + 90? Write an addition with an answer of 20. Write a related addition with an answer of 200. Repeat for two more pairs of numbers that total 20, then 200. © hamilton-trust. org. uk 35 Year 3/4

Problem solving and reasoning answers Year 3 Write 4 number sentences to relate these three numbers: 13, 19 and 6. 13 + 6 = 19, 6 + 13 = 19, 19 - 13 = 6, 19 - 6 = 13 We know 13 + 7 = 20. So, what is 130 + 70? 200 We know 11 + 9 = 20. So, what is 110 + 90? 200 Write an addition with an answer of 20. Write a related addition with an answer of 200. Repeat for two more pairs of numbers that total 20, then 200. e. g. 10 + 10 = 20, 100 + 100 = 200 15 + 5 = 20, 150 + 50 = 200. Do children make the connection between the initial number fact to 20 and the subsequent questions? © hamilton-trust. org. uk 36 Year 3/4

Problem solving and reasoning questions Year 4 Write 4 number sentences to relate these three numbers: 240, 390 and 150. Use a mental method to find: 150 + 50 35 + 65 192 + 6 66 + 29 153 + 39 200 – 52 240 + 550 73 – 25 630 – 150 © hamilton-trust. org. uk 37 Year 3/4

Problem solving and reasoning answers Year 4 Write 4 number sentences to relate these three numbers: 240, 390 and 150. 240 + 150 = 390, 150 + 240 = 390, 390 - 150 = 240, 390 - 240 = 150 Use a mental method to find: 150 + 50 200 35 + 65 100 192 + 6 198 66 + 29 95 153 + 39 192 200 – 52 148 240 + 550 790 73 – 25 48 630 – 150 480 Check children’s strategies- are they best suited for the numbers, for example adding and adjusting (66 + 29), using complements (35 + 65), bridging (73 – 25). Can they explain their choices? © hamilton-trust. org. uk 38 Year 3/4