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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 8 · 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. 1.89 − 9 =
  2. 2.372 − 99 =
  3. 3.81 − 9 =
  4. 4.624 + 99 =
  5. 5.78 + 9 =
  6. 6.73 + 9 =
  7. 7.57 + 29 =
  8. 8.263 + 99 =
  9. 9.40 + 19 =
  10. 10.39 + 9 =
  11. 11.64 + 9 =
  12. 12.408 − 99 =
  13. 13.33 − 19 =
  14. 14.12 + 9 =
  15. 15.419 − 99 =
  16. 16.842 − 99 =
  17. 17.66 + 9 =
  18. 18.62 − 9 =
  19. 19.42 + 19 =
  20. 20.203 + 99 =
  21. 21.25 − 9 =
  22. 22.717 − 99 =
  23. 23.40 − 29 =
  24. 24.66 − 19 =
  25. 25.21 + 19 =
  26. 26.41 + 9 =
  27. 27.844 − 99 =
  28. 28.49 + 9 =
  29. 29.53 − 29 =
  30. 30.55 + 9 =
  31. 31.45 + 9 =
  32. 32.54 − 9 =
  33. 33.54 + 19 =
  34. 34.23 + 19 =
  35. 35.379 + 99 =
  36. 36.774 − 99 =
  37. 37.76 + 19 =
  38. 38.84 − 9 =
  39. 39.61 + 9 =
  40. 40.95 − 19 =

Answer key

  1. 80
  2. 273
  3. 72
  4. 723
  5. 87
  6. 82
  7. 86
  8. 362
  9. 59
  10. 48
  11. 73
  12. 309
  13. 14
  14. 21
  15. 320
  16. 743
  17. 75
  18. 53
  19. 61
  20. 302
  21. 16
  22. 618
  23. 11
  24. 47
  25. 40
  26. 50
  27. 745
  28. 58
  29. 24
  30. 64
  31. 54
  32. 45
  33. 73
  34. 42
  35. 478
  36. 675
  37. 95
  38. 75
  39. 70
  40. 76

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