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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 255 · 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. 1.12 + 29 =
  2. 2.78 + 29 =
  3. 3.35 + 29 =
  4. 4.69 + 29 =
  5. 5.99 − 19 =
  6. 6.79 + 19 =
  7. 7.19 − 9 =
  8. 8.16 + 9 =
  9. 9.65 − 29 =
  10. 10.57 + 19 =
  11. 11.53 − 9 =
  12. 12.20 + 29 =
  13. 13.82 − 9 =
  14. 14.37 − 29 =
  15. 15.41 + 19 =
  16. 16.76 − 9 =
  17. 17.27 + 9 =
  18. 18.73 − 29 =
  19. 19.37 + 29 =
  20. 20.43 + 29 =
  21. 21.42 + 29 =
  22. 22.611 + 99 =
  23. 23.40 + 19 =
  24. 24.39 − 9 =
  25. 25.46 + 9 =
  26. 26.53 + 9 =
  27. 27.41 + 9 =
  28. 28.54 + 9 =
  29. 29.654 + 99 =
  30. 30.28 + 19 =
  31. 31.36 − 29 =
  32. 32.19 + 19 =
  33. 33.48 − 29 =
  34. 34.81 − 9 =
  35. 35.68 − 9 =
  36. 36.53 − 19 =
  37. 37.76 − 19 =
  38. 38.482 + 99 =
  39. 39.40 + 9 =
  40. 40.504 + 99 =

Answer key

  1. 41
  2. 107
  3. 64
  4. 98
  5. 80
  6. 98
  7. 10
  8. 25
  9. 36
  10. 76
  11. 44
  12. 49
  13. 73
  14. 8
  15. 60
  16. 67
  17. 36
  18. 44
  19. 66
  20. 72
  21. 71
  22. 710
  23. 59
  24. 30
  25. 55
  26. 62
  27. 50
  28. 63
  29. 753
  30. 47
  31. 7
  32. 38
  33. 19
  34. 72
  35. 59
  36. 34
  37. 57
  38. 581
  39. 49
  40. 603

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