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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 858 · 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. 1.42 − 9 =
  2. 2.863 − 99 =
  3. 3.35 + 19 =
  4. 4.53 − 9 =
  5. 5.50 + 9 =
  6. 6.26 − 9 =
  7. 7.376 − 99 =
  8. 8.55 − 29 =
  9. 9.20 + 9 =
  10. 10.58 − 19 =
  11. 11.36 + 19 =
  12. 12.21 + 19 =
  13. 13.37 − 9 =
  14. 14.561 − 99 =
  15. 15.18 + 19 =
  16. 16.36 + 9 =
  17. 17.51 − 29 =
  18. 18.548 − 99 =
  19. 19.363 − 99 =
  20. 20.62 − 29 =
  21. 21.533 − 99 =
  22. 22.880 − 99 =
  23. 23.30 − 19 =
  24. 24.163 + 99 =
  25. 25.207 + 99 =
  26. 26.882 − 99 =
  27. 27.585 − 99 =
  28. 28.75 + 9 =
  29. 29.97 − 29 =
  30. 30.63 + 19 =
  31. 31.22 + 29 =
  32. 32.78 + 19 =
  33. 33.20 + 19 =
  34. 34.203 − 99 =
  35. 35.49 − 9 =
  36. 36.801 − 99 =
  37. 37.21 + 9 =
  38. 38.15 + 9 =
  39. 39.30 + 29 =
  40. 40.65 − 29 =

Answer key

  1. 33
  2. 764
  3. 54
  4. 44
  5. 59
  6. 17
  7. 277
  8. 26
  9. 29
  10. 39
  11. 55
  12. 40
  13. 28
  14. 462
  15. 37
  16. 45
  17. 22
  18. 449
  19. 264
  20. 33
  21. 434
  22. 781
  23. 11
  24. 262
  25. 306
  26. 783
  27. 486
  28. 84
  29. 68
  30. 82
  31. 51
  32. 97
  33. 39
  34. 104
  35. 40
  36. 702
  37. 30
  38. 24
  39. 59
  40. 36

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