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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 645 · 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. 1.37 + 9 =
  2. 2.403 + 99 =
  3. 3.101 − 29 =
  4. 4.75 + 29 =
  5. 5.85 − 19 =
  6. 6.579 − 99 =
  7. 7.43 + 29 =
  8. 8.410 − 99 =
  9. 9.377 + 99 =
  10. 10.22 + 29 =
  11. 11.14 + 29 =
  12. 12.65 − 19 =
  13. 13.599 + 99 =
  14. 14.56 + 29 =
  15. 15.53 − 9 =
  16. 16.133 + 99 =
  17. 17.17 + 19 =
  18. 18.192 + 99 =
  19. 19.56 − 29 =
  20. 20.259 + 99 =
  21. 21.106 − 29 =
  22. 22.60 + 19 =
  23. 23.32 + 19 =
  24. 24.20 − 9 =
  25. 25.74 + 9 =
  26. 26.68 + 9 =
  27. 27.21 + 9 =
  28. 28.36 + 19 =
  29. 29.78 + 29 =
  30. 30.77 − 19 =
  31. 31.130 + 99 =
  32. 32.61 − 29 =
  33. 33.47 + 29 =
  34. 34.27 + 19 =
  35. 35.41 + 29 =
  36. 36.374 + 99 =
  37. 37.71 + 9 =
  38. 38.291 − 99 =
  39. 39.94 − 29 =
  40. 40.29 + 19 =

Answer key

  1. 46
  2. 502
  3. 72
  4. 104
  5. 66
  6. 480
  7. 72
  8. 311
  9. 476
  10. 51
  11. 43
  12. 46
  13. 698
  14. 85
  15. 44
  16. 232
  17. 36
  18. 291
  19. 27
  20. 358
  21. 77
  22. 79
  23. 51
  24. 11
  25. 83
  26. 77
  27. 30
  28. 55
  29. 107
  30. 58
  31. 229
  32. 32
  33. 76
  34. 46
  35. 70
  36. 473
  37. 80
  38. 192
  39. 65
  40. 48

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