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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 640 · 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. 1.244 − 99 =
  2. 2.514 + 99 =
  3. 3.66 + 9 =
  4. 4.35 − 9 =
  5. 5.85 − 9 =
  6. 6.32 + 19 =
  7. 7.490 − 99 =
  8. 8.53 + 9 =
  9. 9.48 + 9 =
  10. 10.452 + 99 =
  11. 11.186 + 99 =
  12. 12.37 + 19 =
  13. 13.504 + 99 =
  14. 14.53 − 29 =
  15. 15.15 + 9 =
  16. 16.47 − 9 =
  17. 17.37 − 29 =
  18. 18.75 + 9 =
  19. 19.26 − 9 =
  20. 20.659 − 99 =
  21. 21.631 − 99 =
  22. 22.41 − 9 =
  23. 23.575 − 99 =
  24. 24.303 + 99 =
  25. 25.81 − 29 =
  26. 26.21 + 19 =
  27. 27.702 + 99 =
  28. 28.14 − 9 =
  29. 29.18 − 9 =
  30. 30.100 − 29 =
  31. 31.45 − 19 =
  32. 32.66 − 19 =
  33. 33.32 − 9 =
  34. 34.52 − 9 =
  35. 35.800 − 99 =
  36. 36.22 + 19 =
  37. 37.86 − 19 =
  38. 38.16 + 19 =
  39. 39.464 + 99 =
  40. 40.94 − 29 =

Answer key

  1. 145
  2. 613
  3. 75
  4. 26
  5. 76
  6. 51
  7. 391
  8. 62
  9. 57
  10. 551
  11. 285
  12. 56
  13. 603
  14. 24
  15. 24
  16. 38
  17. 8
  18. 84
  19. 17
  20. 560
  21. 532
  22. 32
  23. 476
  24. 402
  25. 52
  26. 40
  27. 801
  28. 5
  29. 9
  30. 71
  31. 26
  32. 47
  33. 23
  34. 43
  35. 701
  36. 41
  37. 67
  38. 35
  39. 563
  40. 65

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