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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 467 · 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. 1.310 + 99 =
  2. 2.44 + 29 =
  3. 3.45 − 29 =
  4. 4.767 − 99 =
  5. 5.36 − 19 =
  6. 6.39 − 29 =
  7. 7.65 + 29 =
  8. 8.13 + 29 =
  9. 9.245 − 99 =
  10. 10.55 + 29 =
  11. 11.25 + 29 =
  12. 12.58 + 19 =
  13. 13.27 + 29 =
  14. 14.108 − 29 =
  15. 15.44 − 29 =
  16. 16.55 + 19 =
  17. 17.28 − 19 =
  18. 18.69 − 9 =
  19. 19.40 − 29 =
  20. 20.58 − 9 =
  21. 21.58 − 29 =
  22. 22.23 + 29 =
  23. 23.26 + 9 =
  24. 24.24 + 19 =
  25. 25.498 − 99 =
  26. 26.67 + 9 =
  27. 27.885 − 99 =
  28. 28.79 + 9 =
  29. 29.80 − 9 =
  30. 30.18 + 19 =
  31. 31.60 + 9 =
  32. 32.62 − 19 =
  33. 33.31 + 29 =
  34. 34.58 + 9 =
  35. 35.235 + 99 =
  36. 36.68 − 9 =
  37. 37.314 − 99 =
  38. 38.715 + 99 =
  39. 39.261 + 99 =
  40. 40.286 + 99 =

Answer key

  1. 409
  2. 73
  3. 16
  4. 668
  5. 17
  6. 10
  7. 94
  8. 42
  9. 146
  10. 84
  11. 54
  12. 77
  13. 56
  14. 79
  15. 15
  16. 74
  17. 9
  18. 60
  19. 11
  20. 49
  21. 29
  22. 52
  23. 35
  24. 43
  25. 399
  26. 76
  27. 786
  28. 88
  29. 71
  30. 37
  31. 69
  32. 43
  33. 60
  34. 67
  35. 334
  36. 59
  37. 215
  38. 814
  39. 360
  40. 385

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