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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 876 · 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. 1.53 − 29 =
  2. 2.79 − 29 =
  3. 3.471 + 99 =
  4. 4.40 + 29 =
  5. 5.89 − 19 =
  6. 6.44 − 29 =
  7. 7.360 + 99 =
  8. 8.603 + 99 =
  9. 9.504 − 99 =
  10. 10.26 − 9 =
  11. 11.50 − 29 =
  12. 12.31 + 9 =
  13. 13.587 − 99 =
  14. 14.55 + 19 =
  15. 15.661 + 99 =
  16. 16.45 + 9 =
  17. 17.708 − 99 =
  18. 18.74 + 9 =
  19. 19.172 + 99 =
  20. 20.371 + 99 =
  21. 21.28 + 19 =
  22. 22.71 − 19 =
  23. 23.88 − 29 =
  24. 24.74 − 19 =
  25. 25.29 + 29 =
  26. 26.80 + 29 =
  27. 27.37 + 29 =
  28. 28.72 − 9 =
  29. 29.42 − 19 =
  30. 30.54 − 29 =
  31. 31.108 − 29 =
  32. 32.41 − 29 =
  33. 33.75 − 19 =
  34. 34.12 + 29 =
  35. 35.30 + 19 =
  36. 36.72 + 29 =
  37. 37.37 − 29 =
  38. 38.25 + 29 =
  39. 39.40 − 19 =
  40. 40.66 + 19 =

Answer key

  1. 24
  2. 50
  3. 570
  4. 69
  5. 70
  6. 15
  7. 459
  8. 702
  9. 405
  10. 17
  11. 21
  12. 40
  13. 488
  14. 74
  15. 760
  16. 54
  17. 609
  18. 83
  19. 271
  20. 470
  21. 47
  22. 52
  23. 59
  24. 55
  25. 58
  26. 109
  27. 66
  28. 63
  29. 23
  30. 25
  31. 79
  32. 12
  33. 56
  34. 41
  35. 49
  36. 101
  37. 8
  38. 54
  39. 21
  40. 85

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