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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 886 · 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. 1.73 − 29 =
  2. 2.51 + 9 =
  3. 3.50 + 19 =
  4. 4.52 + 9 =
  5. 5.335 + 99 =
  6. 6.49 − 29 =
  7. 7.49 + 9 =
  8. 8.54 − 9 =
  9. 9.19 + 19 =
  10. 10.67 + 9 =
  11. 11.53 + 9 =
  12. 12.58 + 19 =
  13. 13.559 − 99 =
  14. 14.79 + 29 =
  15. 15.317 + 99 =
  16. 16.20 + 9 =
  17. 17.48 + 19 =
  18. 18.63 − 9 =
  19. 19.21 + 9 =
  20. 20.53 + 29 =
  21. 21.39 + 19 =
  22. 22.864 − 99 =
  23. 23.72 + 29 =
  24. 24.29 − 9 =
  25. 25.41 − 19 =
  26. 26.63 + 9 =
  27. 27.657 − 99 =
  28. 28.61 + 9 =
  29. 29.81 − 29 =
  30. 30.159 − 99 =
  31. 31.64 + 19 =
  32. 32.86 − 29 =
  33. 33.80 + 19 =
  34. 34.564 − 99 =
  35. 35.74 + 29 =
  36. 36.58 + 9 =
  37. 37.55 + 29 =
  38. 38.80 − 19 =
  39. 39.77 − 29 =
  40. 40.53 − 19 =

Answer key

  1. 44
  2. 60
  3. 69
  4. 61
  5. 434
  6. 20
  7. 58
  8. 45
  9. 38
  10. 76
  11. 62
  12. 77
  13. 460
  14. 108
  15. 416
  16. 29
  17. 67
  18. 54
  19. 30
  20. 82
  21. 58
  22. 765
  23. 101
  24. 20
  25. 22
  26. 72
  27. 558
  28. 70
  29. 52
  30. 60
  31. 83
  32. 57
  33. 99
  34. 465
  35. 103
  36. 67
  37. 84
  38. 61
  39. 48
  40. 34

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