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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 23 · 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 − 9 =
  2. 2.67 − 29 =
  3. 3.32 − 19 =
  4. 4.24 + 9 =
  5. 5.31 + 19 =
  6. 6.681 + 99 =
  7. 7.897 − 99 =
  8. 8.870 − 99 =
  9. 9.415 + 99 =
  10. 10.102 − 29 =
  11. 11.847 − 99 =
  12. 12.24 − 9 =
  13. 13.32 + 19 =
  14. 14.103 − 29 =
  15. 15.67 + 29 =
  16. 16.64 − 19 =
  17. 17.52 + 29 =
  18. 18.90 − 29 =
  19. 19.51 − 9 =
  20. 20.53 + 19 =
  21. 21.45 + 29 =
  22. 22.38 + 19 =
  23. 23.678 − 99 =
  24. 24.40 − 29 =
  25. 25.161 − 99 =
  26. 26.22 + 19 =
  27. 27.42 + 29 =
  28. 28.66 − 19 =
  29. 29.34 + 29 =
  30. 30.617 − 99 =
  31. 31.56 − 9 =
  32. 32.182 + 99 =
  33. 33.307 + 99 =
  34. 34.167 + 99 =
  35. 35.119 + 99 =
  36. 36.326 + 99 =
  37. 37.101 − 29 =
  38. 38.568 + 99 =
  39. 39.577 − 99 =
  40. 40.16 − 9 =

Answer key

  1. 37
  2. 38
  3. 13
  4. 33
  5. 50
  6. 780
  7. 798
  8. 771
  9. 514
  10. 73
  11. 748
  12. 15
  13. 51
  14. 74
  15. 96
  16. 45
  17. 81
  18. 61
  19. 42
  20. 72
  21. 74
  22. 57
  23. 579
  24. 11
  25. 62
  26. 41
  27. 71
  28. 47
  29. 63
  30. 518
  31. 47
  32. 281
  33. 406
  34. 266
  35. 218
  36. 425
  37. 72
  38. 667
  39. 478
  40. 7

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