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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 869 · 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. 1.91 − 29 =
  2. 2.38 + 19 =
  3. 3.37 + 19 =
  4. 4.52 − 19 =
  5. 5.69 − 9 =
  6. 6.59 − 19 =
  7. 7.34 − 9 =
  8. 8.36 − 9 =
  9. 9.72 + 19 =
  10. 10.54 + 9 =
  11. 11.58 − 9 =
  12. 12.54 + 29 =
  13. 13.19 + 19 =
  14. 14.74 − 9 =
  15. 15.70 − 9 =
  16. 16.461 + 99 =
  17. 17.724 + 99 =
  18. 18.62 − 9 =
  19. 19.711 + 99 =
  20. 20.29 − 9 =
  21. 21.49 + 19 =
  22. 22.21 + 9 =
  23. 23.311 − 99 =
  24. 24.68 + 9 =
  25. 25.36 − 19 =
  26. 26.64 + 29 =
  27. 27.36 + 9 =
  28. 28.72 + 29 =
  29. 29.114 + 99 =
  30. 30.72 − 19 =
  31. 31.371 − 99 =
  32. 32.50 − 9 =
  33. 33.150 + 99 =
  34. 34.71 + 9 =
  35. 35.78 − 9 =
  36. 36.605 + 99 =
  37. 37.94 − 19 =
  38. 38.68 + 19 =
  39. 39.805 − 99 =
  40. 40.20 − 9 =

Answer key

  1. 62
  2. 57
  3. 56
  4. 33
  5. 60
  6. 40
  7. 25
  8. 27
  9. 91
  10. 63
  11. 49
  12. 83
  13. 38
  14. 65
  15. 61
  16. 560
  17. 823
  18. 53
  19. 810
  20. 20
  21. 68
  22. 30
  23. 212
  24. 77
  25. 17
  26. 93
  27. 45
  28. 101
  29. 213
  30. 53
  31. 272
  32. 41
  33. 249
  34. 80
  35. 69
  36. 704
  37. 75
  38. 87
  39. 706
  40. 11

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