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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 989 · 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. 1.59 − 9 =
  2. 2.49 + 29 =
  3. 3.46 + 9 =
  4. 4.86 − 19 =
  5. 5.17 + 19 =
  6. 6.68 + 9 =
  7. 7.78 − 19 =
  8. 8.37 + 29 =
  9. 9.68 + 29 =
  10. 10.12 + 19 =
  11. 11.634 + 99 =
  12. 12.471 + 99 =
  13. 13.98 − 19 =
  14. 14.64 + 19 =
  15. 15.60 − 19 =
  16. 16.50 − 9 =
  17. 17.62 + 29 =
  18. 18.66 − 29 =
  19. 19.47 + 9 =
  20. 20.29 + 29 =
  21. 21.392 − 99 =
  22. 22.29 + 9 =
  23. 23.38 + 29 =
  24. 24.78 + 29 =
  25. 25.97 − 29 =
  26. 26.31 + 9 =
  27. 27.43 − 29 =
  28. 28.19 − 9 =
  29. 29.42 + 29 =
  30. 30.44 + 29 =
  31. 31.707 − 99 =
  32. 32.79 − 29 =
  33. 33.143 + 99 =
  34. 34.51 + 29 =
  35. 35.97 − 19 =
  36. 36.78 + 9 =
  37. 37.74 + 29 =
  38. 38.62 − 19 =
  39. 39.60 + 9 =
  40. 40.88 − 19 =

Answer key

  1. 50
  2. 78
  3. 55
  4. 67
  5. 36
  6. 77
  7. 59
  8. 66
  9. 97
  10. 31
  11. 733
  12. 570
  13. 79
  14. 83
  15. 41
  16. 41
  17. 91
  18. 37
  19. 56
  20. 58
  21. 293
  22. 38
  23. 67
  24. 107
  25. 68
  26. 40
  27. 14
  28. 10
  29. 71
  30. 73
  31. 608
  32. 50
  33. 242
  34. 80
  35. 78
  36. 87
  37. 103
  38. 43
  39. 69
  40. 69

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