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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 71 · 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. 1.47 + 9 =
  2. 2.21 + 19 =
  3. 3.61 + 19 =
  4. 4.74 − 9 =
  5. 5.39 − 29 =
  6. 6.26 + 9 =
  7. 7.551 − 99 =
  8. 8.65 − 29 =
  9. 9.22 − 19 =
  10. 10.55 + 9 =
  11. 11.65 + 19 =
  12. 12.28 − 9 =
  13. 13.53 + 29 =
  14. 14.53 + 9 =
  15. 15.22 + 19 =
  16. 16.26 − 9 =
  17. 17.85 − 9 =
  18. 18.19 + 19 =
  19. 19.34 + 29 =
  20. 20.78 + 9 =
  21. 21.47 + 29 =
  22. 22.65 + 29 =
  23. 23.64 − 19 =
  24. 24.45 − 19 =
  25. 25.35 − 9 =
  26. 26.72 + 19 =
  27. 27.80 + 29 =
  28. 28.24 − 19 =
  29. 29.75 − 29 =
  30. 30.25 + 29 =
  31. 31.39 − 19 =
  32. 32.541 + 99 =
  33. 33.66 + 19 =
  34. 34.43 + 19 =
  35. 35.12 + 19 =
  36. 36.838 − 99 =
  37. 37.42 + 29 =
  38. 38.60 + 9 =
  39. 39.32 + 9 =
  40. 40.64 + 19 =

Answer key

  1. 56
  2. 40
  3. 80
  4. 65
  5. 10
  6. 35
  7. 452
  8. 36
  9. 3
  10. 64
  11. 84
  12. 19
  13. 82
  14. 62
  15. 41
  16. 17
  17. 76
  18. 38
  19. 63
  20. 87
  21. 76
  22. 94
  23. 45
  24. 26
  25. 26
  26. 91
  27. 109
  28. 5
  29. 46
  30. 54
  31. 20
  32. 640
  33. 85
  34. 62
  35. 31
  36. 739
  37. 71
  38. 69
  39. 41
  40. 83

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