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Objectives Day 1 Add 1-digit numbers to 3-digit numbers. Day 2

Addition and Subtraction Mentally add/subtract 1-digit numbers. Objectives Day 1 Add 1-digit numbers to 3-digit numbers. Day 2 Subtract 1-digit numbers from 3-digit numbers. Addition and Subtraction Mentally add/subtract 1-digit numbers. Starters Day 1

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Objectives Day 1 Add 1-digit numbers to 3-digit numbers. Day 2

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  1. Addition and Subtraction Mentally add/subtract 1-digit numbers Objectives Day 1 Add 1-digit numbers to 3-digit numbers. Day 2 Subtract 1-digit numbers from 3-digit numbers. Year 3

  2. Addition and Subtraction Mentally add/subtract 1-digit numbers Starters Day 1 Add any pair of 1–digit numbers (pre-requisite skills) Day 2 Subtract 1-digit numbers from teens numbers (pre-requisite skills) Year 3

  3. Addition and Subtraction Mentally add/subtract 1-digit numbers Starter Add any pair of 1–digit numbers Year 3

  4. Addition and Subtraction Mentally add/subtract 1-digit numbers Starter Subtract 1-digit numbers from teens numbers Year 3

  5. Addition and Subtraction Mentally add/subtract 1-digit numbers Objectives Day 1 Add 1-digit numbers to 3-digit numbers. Year 3

  6. Day 1: Add 1-digit numbers to 3-digit numbers. 347 + 5 Think, pair, share – what different strategies could you use to find 347 + 5? We could just count on 5 from 347… 348, 349, 350, 351, 352, but is there a better way? We could ‘bridge the 10’, adding 5 in two steps: 347 + 3 + 2 = ? We could use number facts: 7 + 5 = 12 so 347 + 5 = 352. Can you see why? Year 3

  7. Day 1: Add 1-digit numbers to 3-digit numbers. 236 + 7 and 878 + 6 Discuss how you can solve these two questions without counting on in 1s. Let’s check 236 + 7 Let’s check 878 + 6 We could use number facts: 8 + 6 = 14 so 878 + 6 = 884 Can you see why? We could ‘bridge the 10’, adding 7 in two steps: 236 + 4 + 3 = ? We could use number facts: 6 + 7 = 13 so 236 + 7 = 243, can you see why? We could ‘bridge the 10’, adding 6 in two steps: 878 + 2 + 4 = ? Year 3

  8. Day 1: Add 1-digit numbers to 3-digit numbers. 397 + 5 and 693 + 9 Discuss how you can solve these two questions without counting on in 1s. This time we cross a 100s number…! Let’s check 397 + 5 Let’s check 693 + 9 We could ‘bridge the 10’, adding 5 in two steps: 397 + 3 + 2 = ? We could ‘bridge the 10’, adding 9 in two steps: 693 + 7 + 2 = ? We could use number facts: 7 + 5 = 12 so 397 + 5 = 402. Can you see why? We could use number facts: 3 + 9 = 12 so 693 + 9 = 702. Can you see why? Year 3

  9. Challenge Year 3

  10. Addition and Subtraction Mentally add/subtract 1-digit numbers Objectives Day 2 Subtract 1-digit numbers from 3-digit numbers. Year 3

  11. Day 2: Subtract 1-digit numbers from 3-digit numbers. 342 - 6 = 336 Think, pair, share – is this answer correct? How do you know? We could just count back 6 from 342… 341, 340, 339, 338, 337, 336, but is there a better way? We could ‘bridge the 10’, subtracting 6 in two steps: 342 - 2 - 4 = ? We could use number facts: 12 - 6 = 6 so 342 - 6 = 336, can you see why? Year 3

  12. Day 2: Subtract 1-digit numbers from 3-digit numbers. Now try 352 - 7 using each of those strategies. Let’s check… We could use number facts: 12 - 7 = 5 so 352 - 7 = 345. Can you see why? We could ‘bridge the 10’, subtracting 7 in two steps: 352 - 2 - 5 = ? Year 3

  13. Day 2: Subtract 1-digit numbers from 3-digit numbers. 352 - 7 = 345. We can check by using the inverse operation! Choose the strategy that works best for you rather than count on or back in 1s. Good mathematicians can spot when to use number facts or bridging 10. What is 345 + 7? We can use one of the strategies for addition we used in the last lesson. On your whiteboards write two other subtractions that involve crossing a multiple of 10. Let’s check some of those… Year 3

  14. Challenge Year 3

  15. Addition and Subtraction Mentally add/subtract 1-digit numbers Well Done! You’ve completed this unit. Objectives Day 1 Add 1-digit numbers to 3-digit numbers. Day 2 Subtract 1-digit numbers from 3-digit numbers. Year 3

  16. Problem solving and reasoning questions Complete the bar models: How many times can 7 be subtracted from 232 before the answer is less than 200? Kit says ‘If I keep adding 6 to 152, I’ll eventually reach exactly 200’. Is he correct? Year 3

  17. Problem solving and reasoning: Answers Complete the bar models: Answers of 349 and 631 for the third and fourth questions respectively result from children adding rather than subtracting the 1-digit number. Other errors may arise from children counting on or back in 1s rather than using number facts to bridge 10s How many times can 7 be subtracted from 232 before the answer is less than 200? 4 times – counting back in 7s from 232: 225, 218, 211, 204, 197. Kit says ‘If I keep adding 6 to 152, I’ll eventually reach exactly 200’. Is he correct? He is - counting on in 6s from 152: 158, 164, 170, 176, 182, 188, 194, 200 Year 3

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