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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 508 · 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. 1.178 − 99 =
  2. 2.68 − 9 =
  3. 3.54 − 29 =
  4. 4.184 − 99 =
  5. 5.786 + 99 =
  6. 6.46 + 9 =
  7. 7.58 − 29 =
  8. 8.44 + 9 =
  9. 9.557 + 99 =
  10. 10.35 + 29 =
  11. 11.61 + 9 =
  12. 12.20 − 9 =
  13. 13.27 − 19 =
  14. 14.32 − 9 =
  15. 15.476 + 99 =
  16. 16.85 − 19 =
  17. 17.556 − 99 =
  18. 18.65 − 9 =
  19. 19.64 − 29 =
  20. 20.40 − 9 =
  21. 21.40 − 29 =
  22. 22.44 − 9 =
  23. 23.764 − 99 =
  24. 24.37 − 19 =
  25. 25.539 − 99 =
  26. 26.83 − 9 =
  27. 27.29 − 19 =
  28. 28.22 − 19 =
  29. 29.54 + 9 =
  30. 30.48 − 9 =
  31. 31.41 + 29 =
  32. 32.76 − 9 =
  33. 33.591 − 99 =
  34. 34.262 + 99 =
  35. 35.393 − 99 =
  36. 36.94 − 29 =
  37. 37.477 − 99 =
  38. 38.65 − 19 =
  39. 39.76 + 9 =
  40. 40.70 − 29 =

Answer key

  1. 79
  2. 59
  3. 25
  4. 85
  5. 885
  6. 55
  7. 29
  8. 53
  9. 656
  10. 64
  11. 70
  12. 11
  13. 8
  14. 23
  15. 575
  16. 66
  17. 457
  18. 56
  19. 35
  20. 31
  21. 11
  22. 35
  23. 665
  24. 18
  25. 440
  26. 74
  27. 10
  28. 3
  29. 63
  30. 39
  31. 70
  32. 67
  33. 492
  34. 361
  35. 294
  36. 65
  37. 378
  38. 46
  39. 85
  40. 41

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