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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 899 · 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. 1.40 + 19 =
  2. 2.25 + 9 =
  3. 3.74 + 29 =
  4. 4.381 − 99 =
  5. 5.25 + 29 =
  6. 6.71 + 9 =
  7. 7.35 + 9 =
  8. 8.452 − 99 =
  9. 9.67 + 19 =
  10. 10.784 − 99 =
  11. 11.24 + 29 =
  12. 12.101 − 29 =
  13. 13.626 + 99 =
  14. 14.81 − 9 =
  15. 15.35 − 29 =
  16. 16.21 + 19 =
  17. 17.46 + 19 =
  18. 18.23 − 9 =
  19. 19.37 + 19 =
  20. 20.82 − 9 =
  21. 21.448 − 99 =
  22. 22.80 − 9 =
  23. 23.14 + 29 =
  24. 24.22 + 19 =
  25. 25.34 − 29 =
  26. 26.56 + 19 =
  27. 27.94 − 19 =
  28. 28.67 + 29 =
  29. 29.81 − 19 =
  30. 30.58 − 19 =
  31. 31.66 + 9 =
  32. 32.65 − 9 =
  33. 33.45 + 9 =
  34. 34.25 − 9 =
  35. 35.52 − 9 =
  36. 36.797 + 99 =
  37. 37.761 + 99 =
  38. 38.533 − 99 =
  39. 39.38 + 29 =
  40. 40.48 − 19 =

Answer key

  1. 59
  2. 34
  3. 103
  4. 282
  5. 54
  6. 80
  7. 44
  8. 353
  9. 86
  10. 685
  11. 53
  12. 72
  13. 725
  14. 72
  15. 6
  16. 40
  17. 65
  18. 14
  19. 56
  20. 73
  21. 349
  22. 71
  23. 43
  24. 41
  25. 5
  26. 75
  27. 75
  28. 96
  29. 62
  30. 39
  31. 75
  32. 56
  33. 54
  34. 16
  35. 43
  36. 896
  37. 860
  38. 434
  39. 67
  40. 29

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