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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 314 · 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. 1.74 + 9 =
  2. 2.80 + 9 =
  3. 3.98 − 19 =
  4. 4.746 − 99 =
  5. 5.78 − 29 =
  6. 6.37 + 29 =
  7. 7.63 + 19 =
  8. 8.79 + 19 =
  9. 9.60 − 9 =
  10. 10.20 + 9 =
  11. 11.57 − 19 =
  12. 12.314 − 99 =
  13. 13.35 + 9 =
  14. 14.12 + 19 =
  15. 15.673 − 99 =
  16. 16.40 − 9 =
  17. 17.17 + 29 =
  18. 18.15 − 9 =
  19. 19.452 − 99 =
  20. 20.96 − 29 =
  21. 21.71 + 9 =
  22. 22.35 + 29 =
  23. 23.85 − 9 =
  24. 24.52 + 19 =
  25. 25.70 + 29 =
  26. 26.372 − 99 =
  27. 27.74 + 29 =
  28. 28.76 − 19 =
  29. 29.76 − 9 =
  30. 30.26 + 29 =
  31. 31.531 + 99 =
  32. 32.622 + 99 =
  33. 33.105 − 29 =
  34. 34.655 + 99 =
  35. 35.29 − 9 =
  36. 36.18 + 9 =
  37. 37.701 + 99 =
  38. 38.20 + 19 =
  39. 39.26 + 19 =
  40. 40.28 + 9 =

Answer key

  1. 83
  2. 89
  3. 79
  4. 647
  5. 49
  6. 66
  7. 82
  8. 98
  9. 51
  10. 29
  11. 38
  12. 215
  13. 44
  14. 31
  15. 574
  16. 31
  17. 46
  18. 6
  19. 353
  20. 67
  21. 80
  22. 64
  23. 76
  24. 71
  25. 99
  26. 273
  27. 103
  28. 57
  29. 67
  30. 55
  31. 630
  32. 721
  33. 76
  34. 754
  35. 20
  36. 27
  37. 800
  38. 39
  39. 45
  40. 37

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