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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 889 · 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. 1.46 + 19 =
  2. 2.239 − 99 =
  3. 3.50 − 29 =
  4. 4.37 + 29 =
  5. 5.216 + 99 =
  6. 6.77 + 29 =
  7. 7.55 − 19 =
  8. 8.29 − 19 =
  9. 9.78 − 9 =
  10. 10.42 − 19 =
  11. 11.46 + 9 =
  12. 12.218 + 99 =
  13. 13.63 − 19 =
  14. 14.342 − 99 =
  15. 15.22 + 29 =
  16. 16.778 − 99 =
  17. 17.54 − 29 =
  18. 18.15 − 9 =
  19. 19.152 − 99 =
  20. 20.35 − 9 =
  21. 21.439 + 99 =
  22. 22.796 + 99 =
  23. 23.344 − 99 =
  24. 24.69 − 9 =
  25. 25.58 + 9 =
  26. 26.55 + 9 =
  27. 27.73 + 9 =
  28. 28.177 + 99 =
  29. 29.531 + 99 =
  30. 30.17 − 9 =
  31. 31.42 − 29 =
  32. 32.136 + 99 =
  33. 33.200 − 99 =
  34. 34.56 − 19 =
  35. 35.14 + 19 =
  36. 36.92 − 19 =
  37. 37.94 − 19 =
  38. 38.418 + 99 =
  39. 39.106 + 99 =
  40. 40.285 + 99 =

Answer key

  1. 65
  2. 140
  3. 21
  4. 66
  5. 315
  6. 106
  7. 36
  8. 10
  9. 69
  10. 23
  11. 55
  12. 317
  13. 44
  14. 243
  15. 51
  16. 679
  17. 25
  18. 6
  19. 53
  20. 26
  21. 538
  22. 895
  23. 245
  24. 60
  25. 67
  26. 64
  27. 82
  28. 276
  29. 630
  30. 8
  31. 13
  32. 235
  33. 101
  34. 37
  35. 33
  36. 73
  37. 75
  38. 517
  39. 205
  40. 384

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