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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 545 · 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. 1.103 − 29 =
  2. 2.65 − 19 =
  3. 3.28 + 29 =
  4. 4.36 − 29 =
  5. 5.36 + 29 =
  6. 6.12 + 19 =
  7. 7.46 + 19 =
  8. 8.495 + 99 =
  9. 9.291 + 99 =
  10. 10.56 − 9 =
  11. 11.629 + 99 =
  12. 12.85 − 19 =
  13. 13.84 − 19 =
  14. 14.636 − 99 =
  15. 15.64 − 19 =
  16. 16.34 + 19 =
  17. 17.659 + 99 =
  18. 18.422 + 99 =
  19. 19.61 + 9 =
  20. 20.27 − 19 =
  21. 21.63 + 9 =
  22. 22.62 + 9 =
  23. 23.37 + 9 =
  24. 24.75 + 29 =
  25. 25.105 − 29 =
  26. 26.15 − 9 =
  27. 27.52 − 19 =
  28. 28.41 − 29 =
  29. 29.30 + 29 =
  30. 30.35 − 19 =
  31. 31.73 − 9 =
  32. 32.18 + 19 =
  33. 33.19 + 19 =
  34. 34.43 − 9 =
  35. 35.35 + 19 =
  36. 36.54 + 29 =
  37. 37.265 − 99 =
  38. 38.446 + 99 =
  39. 39.76 − 29 =
  40. 40.384 − 99 =

Answer key

  1. 74
  2. 46
  3. 57
  4. 7
  5. 65
  6. 31
  7. 65
  8. 594
  9. 390
  10. 47
  11. 728
  12. 66
  13. 65
  14. 537
  15. 45
  16. 53
  17. 758
  18. 521
  19. 70
  20. 8
  21. 72
  22. 71
  23. 46
  24. 104
  25. 76
  26. 6
  27. 33
  28. 12
  29. 59
  30. 16
  31. 64
  32. 37
  33. 38
  34. 34
  35. 54
  36. 83
  37. 166
  38. 545
  39. 47
  40. 285

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