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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 713 · 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. 1.36 + 29 =
  2. 2.39 − 19 =
  3. 3.82 − 29 =
  4. 4.25 + 9 =
  5. 5.73 − 19 =
  6. 6.38 − 9 =
  7. 7.20 + 9 =
  8. 8.44 + 9 =
  9. 9.326 + 99 =
  10. 10.69 + 29 =
  11. 11.35 − 9 =
  12. 12.44 − 19 =
  13. 13.556 + 99 =
  14. 14.22 + 29 =
  15. 15.260 − 99 =
  16. 16.45 − 29 =
  17. 17.431 − 99 =
  18. 18.46 − 19 =
  19. 19.168 + 99 =
  20. 20.769 − 99 =
  21. 21.13 + 9 =
  22. 22.74 − 19 =
  23. 23.247 − 99 =
  24. 24.297 − 99 =
  25. 25.83 − 29 =
  26. 26.55 − 29 =
  27. 27.14 + 9 =
  28. 28.81 − 9 =
  29. 29.85 − 29 =
  30. 30.31 + 19 =
  31. 31.71 + 9 =
  32. 32.64 + 19 =
  33. 33.279 + 99 =
  34. 34.75 + 9 =
  35. 35.72 − 29 =
  36. 36.51 − 29 =
  37. 37.169 − 99 =
  38. 38.64 + 9 =
  39. 39.17 − 9 =
  40. 40.180 + 99 =

Answer key

  1. 65
  2. 20
  3. 53
  4. 34
  5. 54
  6. 29
  7. 29
  8. 53
  9. 425
  10. 98
  11. 26
  12. 25
  13. 655
  14. 51
  15. 161
  16. 16
  17. 332
  18. 27
  19. 267
  20. 670
  21. 22
  22. 55
  23. 148
  24. 198
  25. 54
  26. 26
  27. 23
  28. 72
  29. 56
  30. 50
  31. 80
  32. 83
  33. 378
  34. 84
  35. 43
  36. 22
  37. 70
  38. 73
  39. 8
  40. 279

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