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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 933 · 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. 1.674 − 99 =
  2. 2.16 + 9 =
  3. 3.611 + 99 =
  4. 4.62 − 9 =
  5. 5.25 + 29 =
  6. 6.22 − 19 =
  7. 7.54 + 29 =
  8. 8.37 + 29 =
  9. 9.675 + 99 =
  10. 10.78 + 19 =
  11. 11.759 + 99 =
  12. 12.48 − 19 =
  13. 13.64 + 19 =
  14. 14.17 − 9 =
  15. 15.78 − 29 =
  16. 16.326 + 99 =
  17. 17.313 + 99 =
  18. 18.76 + 19 =
  19. 19.14 + 9 =
  20. 20.46 − 19 =
  21. 21.385 + 99 =
  22. 22.65 − 9 =
  23. 23.477 − 99 =
  24. 24.144 + 99 =
  25. 25.55 + 19 =
  26. 26.379 + 99 =
  27. 27.87 − 19 =
  28. 28.38 − 29 =
  29. 29.675 − 99 =
  30. 30.84 − 19 =
  31. 31.16 − 9 =
  32. 32.294 − 99 =
  33. 33.377 − 99 =
  34. 34.31 + 29 =
  35. 35.18 − 9 =
  36. 36.65 + 19 =
  37. 37.54 − 9 =
  38. 38.24 − 19 =
  39. 39.61 + 29 =
  40. 40.20 + 9 =

Answer key

  1. 575
  2. 25
  3. 710
  4. 53
  5. 54
  6. 3
  7. 83
  8. 66
  9. 774
  10. 97
  11. 858
  12. 29
  13. 83
  14. 8
  15. 49
  16. 425
  17. 412
  18. 95
  19. 23
  20. 27
  21. 484
  22. 56
  23. 378
  24. 243
  25. 74
  26. 478
  27. 68
  28. 9
  29. 576
  30. 65
  31. 7
  32. 195
  33. 278
  34. 60
  35. 9
  36. 84
  37. 45
  38. 5
  39. 90
  40. 29

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