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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 34 · 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. 1.39 − 9 =
  2. 2.14 + 19 =
  3. 3.18 + 29 =
  4. 4.64 + 19 =
  5. 5.27 + 19 =
  6. 6.393 − 99 =
  7. 7.159 + 99 =
  8. 8.25 + 29 =
  9. 9.64 + 9 =
  10. 10.19 + 9 =
  11. 11.31 + 9 =
  12. 12.58 − 9 =
  13. 13.66 + 19 =
  14. 14.622 − 99 =
  15. 15.51 + 29 =
  16. 16.60 + 29 =
  17. 17.740 + 99 =
  18. 18.73 − 19 =
  19. 19.71 + 9 =
  20. 20.35 − 9 =
  21. 21.82 − 29 =
  22. 22.30 − 9 =
  23. 23.20 + 9 =
  24. 24.50 − 29 =
  25. 25.99 − 29 =
  26. 26.28 + 9 =
  27. 27.64 − 29 =
  28. 28.24 + 29 =
  29. 29.417 + 99 =
  30. 30.763 + 99 =
  31. 31.583 − 99 =
  32. 32.107 − 29 =
  33. 33.23 − 19 =
  34. 34.74 + 19 =
  35. 35.59 + 19 =
  36. 36.78 + 19 =
  37. 37.190 + 99 =
  38. 38.19 − 9 =
  39. 39.17 + 9 =
  40. 40.51 + 19 =

Answer key

  1. 30
  2. 33
  3. 47
  4. 83
  5. 46
  6. 294
  7. 258
  8. 54
  9. 73
  10. 28
  11. 40
  12. 49
  13. 85
  14. 523
  15. 80
  16. 89
  17. 839
  18. 54
  19. 80
  20. 26
  21. 53
  22. 21
  23. 29
  24. 21
  25. 70
  26. 37
  27. 35
  28. 53
  29. 516
  30. 862
  31. 484
  32. 78
  33. 4
  34. 93
  35. 78
  36. 97
  37. 289
  38. 10
  39. 26
  40. 70

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