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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 843 · 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. 1.75 − 9 =
  2. 2.108 − 29 =
  3. 3.72 + 19 =
  4. 4.31 + 9 =
  5. 5.611 + 99 =
  6. 6.44 + 19 =
  7. 7.22 − 9 =
  8. 8.707 − 99 =
  9. 9.634 + 99 =
  10. 10.27 + 29 =
  11. 11.86 − 19 =
  12. 12.21 − 9 =
  13. 13.17 + 9 =
  14. 14.589 + 99 =
  15. 15.649 + 99 =
  16. 16.73 − 29 =
  17. 17.156 − 99 =
  18. 18.413 + 99 =
  19. 19.98 − 29 =
  20. 20.59 − 29 =
  21. 21.69 + 9 =
  22. 22.76 − 29 =
  23. 23.42 + 29 =
  24. 24.807 − 99 =
  25. 25.95 − 19 =
  26. 26.120 + 99 =
  27. 27.80 − 19 =
  28. 28.252 + 99 =
  29. 29.713 + 99 =
  30. 30.57 − 9 =
  31. 31.74 − 19 =
  32. 32.39 − 19 =
  33. 33.34 + 9 =
  34. 34.13 − 9 =
  35. 35.371 − 99 =
  36. 36.518 + 99 =
  37. 37.13 + 29 =
  38. 38.34 + 19 =
  39. 39.41 − 29 =
  40. 40.37 − 9 =

Answer key

  1. 66
  2. 79
  3. 91
  4. 40
  5. 710
  6. 63
  7. 13
  8. 608
  9. 733
  10. 56
  11. 67
  12. 12
  13. 26
  14. 688
  15. 748
  16. 44
  17. 57
  18. 512
  19. 69
  20. 30
  21. 78
  22. 47
  23. 71
  24. 708
  25. 76
  26. 219
  27. 61
  28. 351
  29. 812
  30. 48
  31. 55
  32. 20
  33. 43
  34. 4
  35. 272
  36. 617
  37. 42
  38. 53
  39. 12
  40. 28

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