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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 445 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.60 + 29 =
  2. 2.17 + 29 =
  3. 3.445 − 99 =
  4. 4.15 + 19 =
  5. 5.72 + 19 =
  6. 6.169 − 99 =
  7. 7.494 − 99 =
  8. 8.246 + 99 =
  9. 9.158 − 99 =
  10. 10.87 − 19 =
  11. 11.91 − 19 =
  12. 12.896 − 99 =
  13. 13.56 − 9 =
  14. 14.51 + 19 =
  15. 15.27 − 9 =
  16. 16.868 − 99 =
  17. 17.62 + 29 =
  18. 18.587 − 99 =
  19. 19.64 + 19 =
  20. 20.45 + 29 =
  21. 21.76 + 29 =
  22. 22.25 + 9 =
  23. 23.77 − 9 =
  24. 24.100 − 29 =
  25. 25.70 + 29 =
  26. 26.18 + 29 =
  27. 27.52 − 29 =
  28. 28.12 + 9 =
  29. 29.64 + 9 =
  30. 30.44 − 29 =
  31. 31.104 − 29 =
  32. 32.105 − 29 =
  33. 33.523 + 99 =
  34. 34.58 + 19 =
  35. 35.300 − 99 =
  36. 36.321 − 99 =
  37. 37.57 − 9 =
  38. 38.78 + 29 =
  39. 39.69 + 19 =
  40. 40.657 + 99 =

Answer key

  1. 89
  2. 46
  3. 346
  4. 34
  5. 91
  6. 70
  7. 395
  8. 345
  9. 59
  10. 68
  11. 72
  12. 797
  13. 47
  14. 70
  15. 18
  16. 769
  17. 91
  18. 488
  19. 83
  20. 74
  21. 105
  22. 34
  23. 68
  24. 71
  25. 99
  26. 47
  27. 23
  28. 21
  29. 73
  30. 15
  31. 75
  32. 76
  33. 622
  34. 77
  35. 201
  36. 222
  37. 48
  38. 107
  39. 88
  40. 756

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