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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 83 · 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. 1.40 − 19 =
  2. 2.39 + 9 =
  3. 3.20 + 9 =
  4. 4.75 − 29 =
  5. 5.13 − 9 =
  6. 6.443 − 99 =
  7. 7.65 − 29 =
  8. 8.30 + 9 =
  9. 9.643 + 99 =
  10. 10.70 + 9 =
  11. 11.25 + 9 =
  12. 12.79 + 29 =
  13. 13.13 + 19 =
  14. 14.20 − 9 =
  15. 15.23 − 9 =
  16. 16.717 − 99 =
  17. 17.309 + 99 =
  18. 18.51 − 29 =
  19. 19.546 + 99 =
  20. 20.75 − 9 =
  21. 21.89 − 29 =
  22. 22.19 + 29 =
  23. 23.568 − 99 =
  24. 24.29 + 29 =
  25. 25.72 + 29 =
  26. 26.479 + 99 =
  27. 27.37 − 29 =
  28. 28.254 + 99 =
  29. 29.40 + 9 =
  30. 30.35 + 9 =
  31. 31.28 + 29 =
  32. 32.78 − 9 =
  33. 33.41 − 29 =
  34. 34.14 − 9 =
  35. 35.16 + 19 =
  36. 36.760 + 99 =
  37. 37.152 + 99 =
  38. 38.56 − 9 =
  39. 39.86 − 29 =
  40. 40.81 − 29 =

Answer key

  1. 21
  2. 48
  3. 29
  4. 46
  5. 4
  6. 344
  7. 36
  8. 39
  9. 742
  10. 79
  11. 34
  12. 108
  13. 32
  14. 11
  15. 14
  16. 618
  17. 408
  18. 22
  19. 645
  20. 66
  21. 60
  22. 48
  23. 469
  24. 58
  25. 101
  26. 578
  27. 8
  28. 353
  29. 49
  30. 44
  31. 57
  32. 69
  33. 12
  34. 5
  35. 35
  36. 859
  37. 251
  38. 47
  39. 57
  40. 52

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