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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 300 · 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. 1.36 − 29 =
  2. 2.27 + 9 =
  3. 3.61 − 19 =
  4. 4.67 + 19 =
  5. 5.65 + 9 =
  6. 6.427 + 99 =
  7. 7.15 + 29 =
  8. 8.180 + 99 =
  9. 9.16 − 9 =
  10. 10.105 − 29 =
  11. 11.66 + 19 =
  12. 12.73 + 9 =
  13. 13.39 + 29 =
  14. 14.12 + 9 =
  15. 15.485 − 99 =
  16. 16.663 + 99 =
  17. 17.39 − 9 =
  18. 18.43 + 9 =
  19. 19.53 − 9 =
  20. 20.23 + 29 =
  21. 21.80 + 9 =
  22. 22.53 + 19 =
  23. 23.49 − 9 =
  24. 24.30 + 9 =
  25. 25.168 − 99 =
  26. 26.64 + 9 =
  27. 27.72 − 9 =
  28. 28.13 + 19 =
  29. 29.153 − 99 =
  30. 30.23 − 9 =
  31. 31.37 − 9 =
  32. 32.81 − 9 =
  33. 33.80 − 9 =
  34. 34.199 + 99 =
  35. 35.642 − 99 =
  36. 36.94 − 29 =
  37. 37.736 + 99 =
  38. 38.453 + 99 =
  39. 39.44 + 19 =
  40. 40.57 + 9 =

Answer key

  1. 7
  2. 36
  3. 42
  4. 86
  5. 74
  6. 526
  7. 44
  8. 279
  9. 7
  10. 76
  11. 85
  12. 82
  13. 68
  14. 21
  15. 386
  16. 762
  17. 30
  18. 52
  19. 44
  20. 52
  21. 89
  22. 72
  23. 40
  24. 39
  25. 69
  26. 73
  27. 63
  28. 32
  29. 54
  30. 14
  31. 28
  32. 72
  33. 71
  34. 298
  35. 543
  36. 65
  37. 835
  38. 552
  39. 63
  40. 66

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