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## Addition and Subtraction Partitioning and column addition

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**Addition and Subtraction**Partitioning and column addition Objectives Day 1 Add pairs of 2-digit numbers mentally. Add 2-digit numbers to 3-digit numbers using mental strategies. Day 2 Add two 3-digit numbers using compact written addition. Day 3 Add three 3-digit numbers using compact written addition. Year 4**Addition and Subtraction**Partitioning and column addition Starters Day 1Place value in 4-digit and 5-digit numbers (pre-requisite skills) Suggested for Day 2Count in 1/4s and 1/8s (simmering skills) Suggested for Day 3Addition facts to 20 (simmering skills) Year 4**Addition and Subtraction**Partitioning and column addition StarterPlace value in 4-digit and 5-digit numbers Year 4**Addition and Subtraction**Partitioning and column addition StarterCount in 1/4s and 1/8s Year 4**Addition and Subtraction**Partitioning and column addition StarterAddition facts to 20 Year 4**Addition and Subtraction**Partitioning and column addition Objectives Day 1 Add pairs of 2-digit numbers mentally. Add 2-digit numbers to 3-digit numbers using mental strategies. Year 4**Day 1:Add pairs of 2-digit numbers mentally. Add 2-digit**numbers to 3-digit numbers using mental strategies. + Let’s remember how to add 2 numbers by partitioning. 4 8 2 0 4 0 Partition the numbers into 10s and 1s. 2 0 + 4 0 = 6 0 4 8 Add the 10s, then the 1s. 4 0 + = 8 2 1 0 4 2 0 Then add together to find the total. 2 7 0 = 2 6 0 1 0 + Year 4**Day 1:Add pairs of 2-digit numbers mentally. Add 2-digit**numbers to 3-digit numbers using mental strategies. Let’s try 178 + 31. Let’s see how to add a 2-digit number to a 3-digit number. First partition the numbers: 178 = 100 + 70 + 8 and 31 = 30 + 1 Then re-order the 10s and 1s and add: 178 + 31 = 100 + 70 + 30 +8 + 1 = 100 + 100 + 9 = 209 It’s O.K. to do some jottings to help! Year 4**Day 1:Add pairs of 2-digit numbers mentally. Add 2-digit**numbers to 3-digit numbers using mental strategies. 137 + 19 125 + 26 154 + 27 22 + 195 Now look at these 4 questions: What do you think is the most efficient strategy for each? e.g. For 137 + 19 you can add 20 and subtract 1. Talk to your partner… How would you do each one? Try with some jottings. Year 4**Challenge**Year 4**Addition and Subtraction**Partitioning and column addition Objectives Day 2 Add two 3-digit numbers using compact written addition. Year 4**Day 2:Add two 3-digit numbers using compact written**addition. Set the numbers out with 100s, 10s and 1s lined up. Don’t forget the space above the line for any 10s digits from adding 1s or 100s digits from the 10s. Try 324 + 439 on your whiteboards using the compact written method. 324 + 439 324 + 439 1 763 324 + 439 1 63 324 + 439 1 3 First add the 1s. 4 + 9 = ? Look where the digits go. Finally add the 100s. 300 + 400 = ? Next the 10s. 20 + 30 + 10 = ? Don’t forget that last 10. Year 4**Day 2:Add two 3-digit numbers using compact written**addition. 266 + 372 1 638 266 + 372 1 38 266 + 372 Try 246 + 372 on your boards using the written method. Let’s check the steps. Set it out clearly. 266 + 372 8 Next the 10s. 60 + 70 = ? Why is there a 1 under the 300? First add the 1s. 6 + 2 = ? Finally add the 100s. 200 + 300 + 100 = ? Year 4**Challenge**Year 4**Addition and Subtraction**Partitioning and column addition Objectives Day 3 Add three 3-digit numbers using compact written addition. Year 4**Day 3:Add three 3-digit numbers using compact written**addition. Set the numbers out with 100s, 10s and 1s lined up. Don’t forget the space above the line for any 10s digits from adding 1s or 100s digits from the 10s. Try 592 + 235 on your whiteboards using the written method. 592 + 235 592 + 235 1 827 592 + 235 1 27 592 + 235 7 First add the 1s. Place the answer carefully. Finally add the 100s. 500 + 200 + 100. Next the 10s. 90 + 30 = ? Don’t forget the 1 under the 100s. Year 4**Day 3:Add three 3-digit numbers using compact written**addition. Let’s check the steps. 123 474 + 332 123 474 + 332 1 29 123 474 + 332 9 Let’s try the same method to add 3 numbers! 123 474 + 332 1 929 Don’t forget the extra 100! Add the 1s. 3 + 4 + 2 = ? Next the 10s. 20 + 70 + 30 = ? Lastly, the 100s. 100 + 400 + 300 + 100 = ? Year 4**Day 3:Add three 3-digit numbers using compact written**addition. 238 111 + 216 1 5 238 111 + 216 1 65 238 111 + 216 Set it out neatly! Now try 238 + 111 + 216 on your whiteboards. 238 111 + 216 1 565 Add the 1s. 8 + 1 + 6 = 15 Where did you put the digits? Next the 10s. 30 + 10 + 10 + 10 = ? Lastly, the 100s. 200 + 100 + 200 = ? Year 4**Challenge**Year 4**Addition and Subtraction**Partitioning and column addition Well Done! You’ve completed this unit. Objectives Day 1 Add pairs of 2-digit numbers mentally. Add 2-digit numbers to 3-digit numbers using mental strategies. Day 2 Add two 3-digit numbers using compact written addition. Day 3 Add three 3-digit numbers using compact written addition. Year 4**Addition and Subtraction Unit 1**Problem solving and reasoning questions Complete these additions mentally, with only the answer written down! 78 + 127 = and 348 + 39 = Use a different method for each and explain both of your strategies. Write the missing numbers in this calculation: If 378 is subtracted from a number to leave 284, what was the number? Add 375 + 528 + 194 using expanded column addition. Year 4**Problem solving and reasoning answers**Complete these additions mentally, with only the answer written down! 78 + 127 = 205 348 + 39 = 387 78 + 127 Start with the larger number, 127, and solve by partitioning 78, adding 70 then 8. 348 + 39 Add 40 then subtract 1 to adjust. Other strategies are possible, look for coherence in the explanation. Write the missing numbers in this calculation: Add 375 + 528 + 194 using expanded column addition. 1097 Answers such as 987 or 997 suggest children have either forgotten the extra 10 or 100. If 378 is subtracted from a number to leave 284, what was the number? 662. Some children may be confused by the wording and attempt a subtraction. Year 4