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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 214 · 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. 1.203 − 99 =
  2. 2.116 + 99 =
  3. 3.209 + 99 =
  4. 4.15 + 9 =
  5. 5.15 − 9 =
  6. 6.36 − 29 =
  7. 7.237 + 99 =
  8. 8.64 + 9 =
  9. 9.21 + 29 =
  10. 10.64 − 9 =
  11. 11.22 + 29 =
  12. 12.25 + 19 =
  13. 13.648 − 99 =
  14. 14.68 − 9 =
  15. 15.46 + 29 =
  16. 16.29 + 19 =
  17. 17.49 − 29 =
  18. 18.58 − 19 =
  19. 19.38 − 19 =
  20. 20.418 + 99 =
  21. 21.52 − 19 =
  22. 22.18 + 29 =
  23. 23.36 + 19 =
  24. 24.714 − 99 =
  25. 25.52 + 29 =
  26. 26.85 − 9 =
  27. 27.48 + 9 =
  28. 28.40 − 9 =
  29. 29.337 − 99 =
  30. 30.201 − 99 =
  31. 31.539 + 99 =
  32. 32.66 − 9 =
  33. 33.36 + 9 =
  34. 34.39 − 9 =
  35. 35.79 − 19 =
  36. 36.39 + 9 =
  37. 37.50 − 9 =
  38. 38.329 − 99 =
  39. 39.57 − 9 =
  40. 40.53 − 29 =

Answer key

  1. 104
  2. 215
  3. 308
  4. 24
  5. 6
  6. 7
  7. 336
  8. 73
  9. 50
  10. 55
  11. 51
  12. 44
  13. 549
  14. 59
  15. 75
  16. 48
  17. 20
  18. 39
  19. 19
  20. 517
  21. 33
  22. 47
  23. 55
  24. 615
  25. 81
  26. 76
  27. 57
  28. 31
  29. 238
  30. 102
  31. 638
  32. 57
  33. 45
  34. 30
  35. 60
  36. 48
  37. 41
  38. 230
  39. 48
  40. 24

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