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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 283 · 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. 1.29 + 9 =
  2. 2.74 + 9 =
  3. 3.27 + 19 =
  4. 4.289 + 99 =
  5. 5.37 − 19 =
  6. 6.864 − 99 =
  7. 7.34 − 9 =
  8. 8.19 − 9 =
  9. 9.17 − 9 =
  10. 10.59 + 29 =
  11. 11.54 − 9 =
  12. 12.66 − 29 =
  13. 13.126 + 99 =
  14. 14.13 + 29 =
  15. 15.89 − 29 =
  16. 16.274 − 99 =
  17. 17.62 − 19 =
  18. 18.14 + 29 =
  19. 19.115 + 99 =
  20. 20.172 + 99 =
  21. 21.28 + 9 =
  22. 22.73 + 19 =
  23. 23.58 − 19 =
  24. 24.277 + 99 =
  25. 25.409 − 99 =
  26. 26.30 + 29 =
  27. 27.59 + 9 =
  28. 28.54 − 29 =
  29. 29.25 + 19 =
  30. 30.62 − 29 =
  31. 31.298 + 99 =
  32. 32.19 + 19 =
  33. 33.741 + 99 =
  34. 34.50 + 9 =
  35. 35.334 − 99 =
  36. 36.610 − 99 =
  37. 37.22 − 9 =
  38. 38.25 + 9 =
  39. 39.66 + 19 =
  40. 40.17 + 19 =

Answer key

  1. 38
  2. 83
  3. 46
  4. 388
  5. 18
  6. 765
  7. 25
  8. 10
  9. 8
  10. 88
  11. 45
  12. 37
  13. 225
  14. 42
  15. 60
  16. 175
  17. 43
  18. 43
  19. 214
  20. 271
  21. 37
  22. 92
  23. 39
  24. 376
  25. 310
  26. 59
  27. 68
  28. 25
  29. 44
  30. 33
  31. 397
  32. 38
  33. 840
  34. 59
  35. 235
  36. 511
  37. 13
  38. 34
  39. 85
  40. 36

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