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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 939 · 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. 1.566 − 99 =
  2. 2.794 + 99 =
  3. 3.47 − 19 =
  4. 4.74 + 29 =
  5. 5.29 + 19 =
  6. 6.134 + 99 =
  7. 7.28 + 29 =
  8. 8.105 − 29 =
  9. 9.75 − 19 =
  10. 10.76 + 9 =
  11. 11.389 + 99 =
  12. 12.68 + 9 =
  13. 13.52 − 29 =
  14. 14.50 + 29 =
  15. 15.109 + 99 =
  16. 16.201 + 99 =
  17. 17.56 − 29 =
  18. 18.35 + 29 =
  19. 19.55 − 29 =
  20. 20.47 + 19 =
  21. 21.65 − 19 =
  22. 22.83 − 29 =
  23. 23.79 + 19 =
  24. 24.298 − 99 =
  25. 25.54 + 9 =
  26. 26.84 − 19 =
  27. 27.789 + 99 =
  28. 28.89 − 9 =
  29. 29.59 − 19 =
  30. 30.18 − 9 =
  31. 31.319 + 99 =
  32. 32.70 − 9 =
  33. 33.43 + 19 =
  34. 34.20 + 29 =
  35. 35.93 − 29 =
  36. 36.41 − 19 =
  37. 37.33 + 29 =
  38. 38.404 − 99 =
  39. 39.524 + 99 =
  40. 40.96 − 29 =

Answer key

  1. 467
  2. 893
  3. 28
  4. 103
  5. 48
  6. 233
  7. 57
  8. 76
  9. 56
  10. 85
  11. 488
  12. 77
  13. 23
  14. 79
  15. 208
  16. 300
  17. 27
  18. 64
  19. 26
  20. 66
  21. 46
  22. 54
  23. 98
  24. 199
  25. 63
  26. 65
  27. 888
  28. 80
  29. 40
  30. 9
  31. 418
  32. 61
  33. 62
  34. 49
  35. 64
  36. 22
  37. 62
  38. 305
  39. 623
  40. 67

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