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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 845 · 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. 1.291 − 99 =
  2. 2.72 − 9 =
  3. 3.58 − 9 =
  4. 4.294 + 99 =
  5. 5.30 − 9 =
  6. 6.40 − 29 =
  7. 7.58 + 29 =
  8. 8.79 − 19 =
  9. 9.60 + 29 =
  10. 10.38 + 19 =
  11. 11.48 + 9 =
  12. 12.15 − 9 =
  13. 13.51 − 29 =
  14. 14.847 − 99 =
  15. 15.42 + 9 =
  16. 16.69 + 9 =
  17. 17.87 − 9 =
  18. 18.31 + 9 =
  19. 19.25 − 9 =
  20. 20.22 + 19 =
  21. 21.43 − 9 =
  22. 22.43 + 29 =
  23. 23.100 − 29 =
  24. 24.28 + 9 =
  25. 25.17 + 19 =
  26. 26.44 + 19 =
  27. 27.55 − 19 =
  28. 28.277 + 99 =
  29. 29.34 − 19 =
  30. 30.480 + 99 =
  31. 31.70 − 29 =
  32. 32.425 + 99 =
  33. 33.52 − 29 =
  34. 34.416 − 99 =
  35. 35.29 + 19 =
  36. 36.503 + 99 =
  37. 37.152 + 99 =
  38. 38.25 − 19 =
  39. 39.81 − 9 =
  40. 40.78 − 9 =

Answer key

  1. 192
  2. 63
  3. 49
  4. 393
  5. 21
  6. 11
  7. 87
  8. 60
  9. 89
  10. 57
  11. 57
  12. 6
  13. 22
  14. 748
  15. 51
  16. 78
  17. 78
  18. 40
  19. 16
  20. 41
  21. 34
  22. 72
  23. 71
  24. 37
  25. 36
  26. 63
  27. 36
  28. 376
  29. 15
  30. 579
  31. 41
  32. 524
  33. 23
  34. 317
  35. 48
  36. 602
  37. 251
  38. 6
  39. 72
  40. 69

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