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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 529 · 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. 1.89 − 9 =
  2. 2.46 + 19 =
  3. 3.58 + 19 =
  4. 4.19 + 29 =
  5. 5.54 − 19 =
  6. 6.76 + 9 =
  7. 7.73 + 29 =
  8. 8.16 − 9 =
  9. 9.525 + 99 =
  10. 10.96 − 29 =
  11. 11.68 + 29 =
  12. 12.60 + 29 =
  13. 13.87 − 9 =
  14. 14.797 + 99 =
  15. 15.78 + 19 =
  16. 16.34 + 19 =
  17. 17.69 − 19 =
  18. 18.537 + 99 =
  19. 19.59 + 9 =
  20. 20.22 − 19 =
  21. 21.682 + 99 =
  22. 22.789 + 99 =
  23. 23.52 − 19 =
  24. 24.39 + 19 =
  25. 25.53 − 29 =
  26. 26.161 − 99 =
  27. 27.367 + 99 =
  28. 28.14 + 29 =
  29. 29.74 + 29 =
  30. 30.32 + 19 =
  31. 31.26 + 19 =
  32. 32.53 − 9 =
  33. 33.46 + 29 =
  34. 34.62 + 29 =
  35. 35.109 − 29 =
  36. 36.26 + 29 =
  37. 37.44 − 19 =
  38. 38.37 + 19 =
  39. 39.68 + 19 =
  40. 40.80 − 9 =

Answer key

  1. 80
  2. 65
  3. 77
  4. 48
  5. 35
  6. 85
  7. 102
  8. 7
  9. 624
  10. 67
  11. 97
  12. 89
  13. 78
  14. 896
  15. 97
  16. 53
  17. 50
  18. 636
  19. 68
  20. 3
  21. 781
  22. 888
  23. 33
  24. 58
  25. 24
  26. 62
  27. 466
  28. 43
  29. 103
  30. 51
  31. 45
  32. 44
  33. 75
  34. 91
  35. 80
  36. 55
  37. 25
  38. 56
  39. 87
  40. 71

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