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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 551 · 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. 1.13 − 9 =
  2. 2.15 − 9 =
  3. 3.55 − 9 =
  4. 4.22 + 29 =
  5. 5.162 + 99 =
  6. 6.73 − 9 =
  7. 7.79 − 29 =
  8. 8.99 − 29 =
  9. 9.95 − 19 =
  10. 10.31 + 29 =
  11. 11.78 + 9 =
  12. 12.87 − 29 =
  13. 13.756 + 99 =
  14. 14.35 − 29 =
  15. 15.65 − 9 =
  16. 16.453 − 99 =
  17. 17.14 + 9 =
  18. 18.46 − 29 =
  19. 19.16 + 9 =
  20. 20.122 + 99 =
  21. 21.24 + 29 =
  22. 22.577 − 99 =
  23. 23.43 + 9 =
  24. 24.63 + 19 =
  25. 25.39 + 19 =
  26. 26.580 + 99 =
  27. 27.63 + 9 =
  28. 28.32 − 29 =
  29. 29.611 − 99 =
  30. 30.34 + 19 =
  31. 31.27 + 9 =
  32. 32.50 − 19 =
  33. 33.33 − 9 =
  34. 34.74 − 9 =
  35. 35.84 − 29 =
  36. 36.40 + 9 =
  37. 37.84 − 19 =
  38. 38.90 − 19 =
  39. 39.64 − 19 =
  40. 40.42 + 9 =

Answer key

  1. 4
  2. 6
  3. 46
  4. 51
  5. 261
  6. 64
  7. 50
  8. 70
  9. 76
  10. 60
  11. 87
  12. 58
  13. 855
  14. 6
  15. 56
  16. 354
  17. 23
  18. 17
  19. 25
  20. 221
  21. 53
  22. 478
  23. 52
  24. 82
  25. 58
  26. 679
  27. 72
  28. 3
  29. 512
  30. 53
  31. 36
  32. 31
  33. 24
  34. 65
  35. 55
  36. 49
  37. 65
  38. 71
  39. 45
  40. 51

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