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Objectives Day 1 Double 2-digit numbers up to 50.

Fractions Doubling and Halving and the concept of a half. Objectives Day 1 Double 2-digit numbers up to 50. Double and halve 2-digit numbers, including odd numbers Day 2 Halve even 2-digit numbers. Double and halve 3-digit numbers. Day 3

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Objectives Day 1 Double 2-digit numbers up to 50.

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  1. Fractions Doubling and Halving and the concept of a half Objectives Day 1 Double 2-digit numbers up to 50. Double and halve 2-digit numbers, including odd numbers Day 2 Halve even 2-digit numbers. Double and halve 3-digit numbers. Day 3 Halve odd numbers with even tens digits, e.g. 25 and 65. Halve odd numbers with odd tens digits, e.g. 35 and 75. Year 3/4

  2. Fractions Doubling and Halving and the concept of a half Short Mental Workouts Day 1 Doubles to 20 Day 2 Halve multiples of 10 Day 3 Count in 5s and 10s Year 3/4

  3. Fractions Doubling and Halving and the concept of a half Short Mental Workout Doubles to 20 Year 3/4

  4. Fractions Doubling and Halving and the concept of a half Short Mental Workout Halve multiples of 10 Year 3/4

  5. Fractions Doubling and Halving and the concept of a half Short Mental Workout Count in 5s and 10s Year 3/4

  6. Fractions Doubling and Halving and the concept of a half Objectives Day 1 Double 2-digit numbers up to 50. Double and halve 2-digit numbers, including odd numbers. Year 3/4

  7. Day 1: Double 2-digit numbers up to 50; Double and halve 2-digit numbers, including odd numbers. 7 8 14 12 60 16 100 160 40 18 6 6 3 Let’s revise some doubles... 8 4 9 20 50 30 80 Year 3/4

  8. Day 1: Double 2-digit numbers up to 50; Double and halve 2-digit numbers, including odd numbers. Let’s see how we can double 26. 26 First partition 26… 20 + 6 Then recombine. 40 + 12 = 52 Double each number... Double 26 is 52. Year 3/4

  9. Day 1: Double 2-digit numbers up to 50; Double and halve 2-digit numbers, including odd numbers. Let’s try doubling 35 together… 35 First partition 35… 30 + 5 Then recombine. 60 + 10 = 70 Double each number... Double 35 is 70. Year 3/4

  10. Day 1: Double 2-digit numbers up to 50; Double and halve 2-digit numbers, including odd numbers. Now let’s try 47… 47 First partition 47… 40 + 7 Then recombine. 80 + 14 = 94 Double each number… Double 47 is 94. Year 3/4

  11. Challenge Year 3/4

  12. Day 1: Double 2-digit numbers up to 50. Now let’s find double 34using place value cards. Work in pairs: each of you make 34 with your cards… 3 0 3 0 6 0 4 8 4 4 4 4 8 8 4 Partition the numbers. Remember: partition  double 10s and 1s  recombine Double 10s and 1s. + = 6 0 3 0 3 0 6 0 3 0 3 0 + = Then recombine. = + Year 3/4

  13. Day 1: Double 2-digit numbers up to 50. Now let’s find double 46using place value cards. 1 0 4 0 4 0 9 0 1 0 2 2 6 6 2 6 6 6 6 Partition the numbers. Double the 10s and 1s. + = 4 0 4 0 8 0 4 0 4 0 8 0 + = Then recombine. = + Year 3/4

  14. Day 1: Double 2-digit numbers up to 50. Let’s check that with a jotting... 46 First partition 46… 40 + 6 Then recombine. 80 + 12 = 92 Double each number... Double 46 is 92. Year 3/4

  15. Day 1: Double 2-digit numbers up to 50. Now try 57. 57 First partition 57… 50 + 7 Then recombine. 100 + 14 = 114 Double each number... Double 57 is 114. Year 3/4

  16. Challenge Year 3/4

  17. Fractions Doubling and Halving and the concept of a half Objectives Day 2 Halve even 2-digit numbers. Double and halve 3-digit numbers. Year 3/4

  18. Day 2: Halve even 2-digit numbers; Double and halve 3-digit numbers. The shop has a half price sale on today, so we need to work out how much the chocolates will cost! Year 3/4

  19. Day 2: Halve even 2-digit numbers; Double and halve 3-digit numbers. Let’s see how to find half of 54p. 54p First partition 54… 50 + 4 Then recombine. 25 + 2 = 27p Halve each number... 27p in the half price sale! Year 3/4

  20. Day 2: Halve even 2-digit numbers; Double and halve 3-digit numbers. Let’s see how to find half of 38p. 38p First partition 38… 30 + 8 Then recombine. 15 + 4 = 19p Halve each number... 19p in the half price sale! Year 3/4

  21. Challenge Year 3/4

  22. Day 2: Double and halve 3-digit numbers. 100 100 150 200 450 250 400 300 350 50 Let’s check through halves of 100s. 200 300 400 500 We can use these number facts to help us double and halve 3-digit numbers! 600 700 800 900 Year 3/4

  23. Day 2: Double and halve 3-digit numbers. Let’s try double 226. Partition and double each part. 400 40 12 400 + 40 + 12 = 452 Double 200 is ? Double 20 is ? 226 Now on your whiteboards find double 471 and double 638. Double 6 is ? Three numbers to add this time! Year 3/4

  24. Day 2: Double and halve 3-digit numbers. Who can talk us through this one? 800 140 2 800 + 140 + 2 = 942 And this one? 471 638 Careful with the addition! 1200 60 16 1200 + 60 + 16 = 1276 Year 3/4

  25. Day 2: Double and halve 3-digit numbers. We can halve 3-digit numbers in the same way. 100 10 3 Half of 200 is ? 100 + 10 + 3 = 113 Half of 20 is ? Half of 6 is ? 226 Now on your whiteboards find half of 576 and 357. Half of 226 is ? Year 3/4

  26. Day 2: Double and halve 3-digit numbers. Who can talk through halving 576? 250 35 3 250 + 35 + 3 = 288 And half of 357? 576 357 150 25 31/2 Careful halving odd numbers! 150 + 25 + 31/2 = 1781/2 Year 3/4

  27. Challenge Year 3/4

  28. Fractions Doubling and Halving and the concept of a half Objectives Day 3 Halve odd numbers with even tens digits, e.g. 25 and 65. Halve odd numbers with odd tens digits, e.g. 35 and 75. Year 3/4

  29. Day 3: Halve odd numbers with even tens digits, e.g. 25 and 65; Halve odd numbers with odd tens digits, e.g. 35 and 75. 40 10 30 35 15 20 25 45 20 60 Let’s halve multiples of 10, write them on your whiteboards… 30 80 90 40 70 50 Year 3/4

  30. Day 3: Halve odd numbers with even tens digits, e.g. 25 and 65; Halve odd numbers with odd tens digits, e.g. 35 and 75. … we can partition and halve, then add. Let’s check those... Talk to your partner. How can we find half of 48, 32 and 56? 20 4 15 1 25 3 20 + 4 =24 15 + 1 = 16 25 + 3 = 28 48 56 32 Year 3/4

  31. Day 3: Halve odd numbers with even tens digits, e.g. 25 and 65; Halve odd numbers with odd tens digits, e.g. 35 and 75. Now let’s see what happens when the 1s digit is odd. 20 21/2 20 + 21/2 = 221/2 45 Now on your whiteboards find half of 37. • How can you halve the odd 1s digit? Year 3/4

  32. Day 3: Halve odd numbers with even tens digits, e.g. 25 and 65; Halve odd numbers with odd tens digits, e.g. 35 and 75. Let’s check half of 37… Who can talk it through? 15 31/2 37 15 + 31/2 = 181/2 Year 4

  33. Challenge Year 3/4

  34. Day 3: Halve odd numbers with even tens digits, e.g. 25 and 65. Work in pairs to halve each of the single-digit odd numbers 3, 5, 7 and 9. What do you notice about this sequence? Let’s check… 11/2 21/2 31/2 41/2 Half of an odd number always ends in 1/2 Year 3/4

  35. Day 3: Halve odd numbers with even tens digits, e.g. 25 and 65. Work in pairs to halve each of 5, 25, 45 and 65. Can you describe any patterns you notice? Let’s check… 21/2 121/2 221/2 321/2 What did you notice? Year 3/4

  36. Challenge Year 3/4

  37. Fractions Doubling and Halving and the concept of a half Well Done! You’ve completed this unit. Objectives Day 1 Double 2-digit numbers up to 50. Double and halve 2-digit numbers, including odd numbers Day 2 Halve even 2-digit numbers. Double and halve 3-digit numbers. Day 3 Halve odd numbers with even tens digits, e.g. 25 and 65. Halve odd numbers with odd tens digits, e.g. 35 and 75. Year 3/4

  38. Problem solving and reasoning questions Year 3 Start at 3 and keep doubling until your answer is close to 100 but NOT over. How many doubles did you write? Repeat, starting at 4. How many this time? Write the missing number(s) in these bar diagrams: Starting with 72, keep halving until you reach a 1-digit number. What is half of that number? Year 3/4

  39. Problem solving and reasoning answers Year 3 Start at 3 and keep doubling until your answer is close to 100 but NOT over. How many doubles did you write? 5 – the sequence is 6, 12, 24, 48, 96 Repeat, starting at 4. How many this time? 8, 16, 32, 64. Write the missing number(s) in these bar diagrams: Mistakes may be due to not partitioning correctly to double and halve 2-digit numbers, for example giving an answer of 66 for the first of these or 21 for the second Starting with 72, keep halving until you reach a 1-digit number. What is half of that number? 41/2 The sequence is 36, 18, 9 then 41/2. Not all children may be confident halving an odd number. Year 3/4

  40. Problem solving and reasoning questions Year 4 Write two sentences to relate these three numbers: 37, 74 and 148. Use a jotting to double these numbers: i) 216 ii) 327 iii) 438 Describe any pattern in the answers Starting with 576, keep halving until you reach a 1-digit number. What is half of that number? Year 3/4

  41. Problem solving and reasoning answers Year 4 Write two sentences to relate these three numbers: 37, 74 and 148. 2 x 37 = 74 and 2 x 74 = 148 Use a jotting to double these numbers: i) 216 432 ii) 327 654 iii) 438 876 Describe any pattern in the answers. The differences between the initial numbers is 111, the answers have a difference of 222. Where children have made errors with doubling 3-digit number it is often the result of treating digits of the number as a single digit, ignoring place value. This would produce an answer of 18 or 34 for (a). It is useful to get children to estimate first. Starting with 576, keep halving until you reach a 1-digit number. What is half of that number? 41/2 The sequence is 288, 144, 72, 36, 18, 9 then 41/2. Year 3/4

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