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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 953 · 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. 1.36 − 19 =
  2. 2.617 − 99 =
  3. 3.337 + 99 =
  4. 4.60 − 29 =
  5. 5.78 + 19 =
  6. 6.557 + 99 =
  7. 7.56 + 19 =
  8. 8.33 + 9 =
  9. 9.60 + 19 =
  10. 10.55 + 29 =
  11. 11.74 + 9 =
  12. 12.39 + 9 =
  13. 13.26 + 19 =
  14. 14.77 + 9 =
  15. 15.100 − 29 =
  16. 16.773 − 99 =
  17. 17.90 − 19 =
  18. 18.30 + 19 =
  19. 19.226 − 99 =
  20. 20.734 + 99 =
  21. 21.138 + 99 =
  22. 22.39 + 29 =
  23. 23.198 + 99 =
  24. 24.260 + 99 =
  25. 25.28 + 29 =
  26. 26.18 + 19 =
  27. 27.79 + 9 =
  28. 28.74 + 29 =
  29. 29.24 + 19 =
  30. 30.57 − 19 =
  31. 31.65 + 29 =
  32. 32.86 − 29 =
  33. 33.71 + 9 =
  34. 34.22 − 19 =
  35. 35.79 − 29 =
  36. 36.46 − 29 =
  37. 37.15 + 19 =
  38. 38.13 + 19 =
  39. 39.93 − 29 =
  40. 40.740 + 99 =

Answer key

  1. 17
  2. 518
  3. 436
  4. 31
  5. 97
  6. 656
  7. 75
  8. 42
  9. 79
  10. 84
  11. 83
  12. 48
  13. 45
  14. 86
  15. 71
  16. 674
  17. 71
  18. 49
  19. 127
  20. 833
  21. 237
  22. 68
  23. 297
  24. 359
  25. 57
  26. 37
  27. 88
  28. 103
  29. 43
  30. 38
  31. 94
  32. 57
  33. 80
  34. 3
  35. 50
  36. 17
  37. 34
  38. 32
  39. 64
  40. 839

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