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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 762 · 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. 1.28 + 19 =
  2. 2.107 − 29 =
  3. 3.796 − 99 =
  4. 4.16 − 9 =
  5. 5.73 − 9 =
  6. 6.566 + 99 =
  7. 7.74 − 29 =
  8. 8.647 + 99 =
  9. 9.53 + 9 =
  10. 10.12 + 19 =
  11. 11.98 − 19 =
  12. 12.28 − 19 =
  13. 13.29 + 9 =
  14. 14.342 + 99 =
  15. 15.86 − 9 =
  16. 16.18 + 9 =
  17. 17.48 + 29 =
  18. 18.396 + 99 =
  19. 19.23 − 19 =
  20. 20.69 − 29 =
  21. 21.185 + 99 =
  22. 22.246 − 99 =
  23. 23.645 + 99 =
  24. 24.59 + 19 =
  25. 25.36 + 9 =
  26. 26.470 + 99 =
  27. 27.788 + 99 =
  28. 28.14 + 19 =
  29. 29.17 + 9 =
  30. 30.63 + 19 =
  31. 31.39 + 29 =
  32. 32.399 + 99 =
  33. 33.71 + 29 =
  34. 34.52 + 29 =
  35. 35.21 + 19 =
  36. 36.85 − 9 =
  37. 37.58 + 9 =
  38. 38.81 − 29 =
  39. 39.31 + 19 =
  40. 40.77 + 29 =

Answer key

  1. 47
  2. 78
  3. 697
  4. 7
  5. 64
  6. 665
  7. 45
  8. 746
  9. 62
  10. 31
  11. 79
  12. 9
  13. 38
  14. 441
  15. 77
  16. 27
  17. 77
  18. 495
  19. 4
  20. 40
  21. 284
  22. 147
  23. 744
  24. 78
  25. 45
  26. 569
  27. 887
  28. 33
  29. 26
  30. 82
  31. 68
  32. 498
  33. 100
  34. 81
  35. 40
  36. 76
  37. 67
  38. 52
  39. 50
  40. 106

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