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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 110 · 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. 1.63 + 29 =
  2. 2.30 + 29 =
  3. 3.78 − 19 =
  4. 4.525 + 99 =
  5. 5.73 + 9 =
  6. 6.33 − 29 =
  7. 7.39 − 29 =
  8. 8.257 + 99 =
  9. 9.61 + 29 =
  10. 10.67 + 9 =
  11. 11.57 + 19 =
  12. 12.53 + 29 =
  13. 13.15 + 9 =
  14. 14.35 − 29 =
  15. 15.71 − 29 =
  16. 16.68 + 19 =
  17. 17.69 + 19 =
  18. 18.77 − 19 =
  19. 19.29 + 19 =
  20. 20.72 − 9 =
  21. 21.50 + 19 =
  22. 22.662 − 99 =
  23. 23.69 − 19 =
  24. 24.683 − 99 =
  25. 25.73 − 9 =
  26. 26.256 + 99 =
  27. 27.27 + 19 =
  28. 28.70 + 19 =
  29. 29.362 − 99 =
  30. 30.185 − 99 =
  31. 31.76 + 19 =
  32. 32.28 + 19 =
  33. 33.48 − 9 =
  34. 34.32 − 9 =
  35. 35.252 − 99 =
  36. 36.764 − 99 =
  37. 37.44 − 19 =
  38. 38.71 + 29 =
  39. 39.71 + 19 =
  40. 40.72 − 19 =

Answer key

  1. 92
  2. 59
  3. 59
  4. 624
  5. 82
  6. 4
  7. 10
  8. 356
  9. 90
  10. 76
  11. 76
  12. 82
  13. 24
  14. 6
  15. 42
  16. 87
  17. 88
  18. 58
  19. 48
  20. 63
  21. 69
  22. 563
  23. 50
  24. 584
  25. 64
  26. 355
  27. 46
  28. 89
  29. 263
  30. 86
  31. 95
  32. 47
  33. 39
  34. 23
  35. 153
  36. 665
  37. 25
  38. 100
  39. 90
  40. 53

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