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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 761 · 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. 1.40 + 29 =
  2. 2.828 − 99 =
  3. 3.38 − 19 =
  4. 4.403 + 99 =
  5. 5.419 − 99 =
  6. 6.28 − 9 =
  7. 7.58 − 9 =
  8. 8.71 − 29 =
  9. 9.32 + 29 =
  10. 10.577 + 99 =
  11. 11.54 − 9 =
  12. 12.35 − 19 =
  13. 13.20 + 19 =
  14. 14.54 − 19 =
  15. 15.112 + 99 =
  16. 16.15 − 9 =
  17. 17.320 − 99 =
  18. 18.42 + 29 =
  19. 19.153 + 99 =
  20. 20.826 − 99 =
  21. 21.542 + 99 =
  22. 22.58 + 19 =
  23. 23.45 − 29 =
  24. 24.235 + 99 =
  25. 25.24 − 9 =
  26. 26.14 + 9 =
  27. 27.15 + 29 =
  28. 28.422 − 99 =
  29. 29.56 + 19 =
  30. 30.187 + 99 =
  31. 31.218 + 99 =
  32. 32.768 + 99 =
  33. 33.34 + 19 =
  34. 34.53 − 9 =
  35. 35.523 + 99 =
  36. 36.458 + 99 =
  37. 37.64 + 19 =
  38. 38.702 + 99 =
  39. 39.77 − 9 =
  40. 40.70 + 19 =

Answer key

  1. 69
  2. 729
  3. 19
  4. 502
  5. 320
  6. 19
  7. 49
  8. 42
  9. 61
  10. 676
  11. 45
  12. 16
  13. 39
  14. 35
  15. 211
  16. 6
  17. 221
  18. 71
  19. 252
  20. 727
  21. 641
  22. 77
  23. 16
  24. 334
  25. 15
  26. 23
  27. 44
  28. 323
  29. 75
  30. 286
  31. 317
  32. 867
  33. 53
  34. 44
  35. 622
  36. 557
  37. 83
  38. 801
  39. 68
  40. 89

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