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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 41 · 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. 1.848 − 99 =
  2. 2.66 − 9 =
  3. 3.31 + 29 =
  4. 4.26 − 9 =
  5. 5.291 + 99 =
  6. 6.40 − 9 =
  7. 7.34 − 29 =
  8. 8.21 − 9 =
  9. 9.40 + 29 =
  10. 10.64 − 9 =
  11. 11.71 + 29 =
  12. 12.91 − 19 =
  13. 13.49 − 19 =
  14. 14.61 + 9 =
  15. 15.18 − 9 =
  16. 16.65 − 9 =
  17. 17.43 + 29 =
  18. 18.485 + 99 =
  19. 19.102 − 29 =
  20. 20.337 − 99 =
  21. 21.28 − 9 =
  22. 22.49 + 9 =
  23. 23.79 − 29 =
  24. 24.604 − 99 =
  25. 25.48 + 9 =
  26. 26.260 + 99 =
  27. 27.13 + 19 =
  28. 28.51 − 29 =
  29. 29.540 − 99 =
  30. 30.74 − 19 =
  31. 31.562 + 99 =
  32. 32.21 + 29 =
  33. 33.89 − 9 =
  34. 34.585 + 99 =
  35. 35.86 − 19 =
  36. 36.69 + 19 =
  37. 37.712 + 99 =
  38. 38.73 − 19 =
  39. 39.29 + 29 =
  40. 40.51 + 19 =

Answer key

  1. 749
  2. 57
  3. 60
  4. 17
  5. 390
  6. 31
  7. 5
  8. 12
  9. 69
  10. 55
  11. 100
  12. 72
  13. 30
  14. 70
  15. 9
  16. 56
  17. 72
  18. 584
  19. 73
  20. 238
  21. 19
  22. 58
  23. 50
  24. 505
  25. 57
  26. 359
  27. 32
  28. 22
  29. 441
  30. 55
  31. 661
  32. 50
  33. 80
  34. 684
  35. 67
  36. 88
  37. 811
  38. 54
  39. 58
  40. 70

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