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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 960 · 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. 1.15 − 9 =
  2. 2.800 + 99 =
  3. 3.17 + 9 =
  4. 4.66 + 9 =
  5. 5.39 + 19 =
  6. 6.32 − 9 =
  7. 7.47 − 29 =
  8. 8.100 − 29 =
  9. 9.79 + 29 =
  10. 10.36 + 9 =
  11. 11.35 + 9 =
  12. 12.52 + 19 =
  13. 13.28 + 29 =
  14. 14.60 + 29 =
  15. 15.202 − 99 =
  16. 16.65 − 29 =
  17. 17.80 − 19 =
  18. 18.81 − 29 =
  19. 19.18 + 19 =
  20. 20.31 − 19 =
  21. 21.12 + 29 =
  22. 22.67 − 29 =
  23. 23.316 − 99 =
  24. 24.455 + 99 =
  25. 25.36 + 19 =
  26. 26.29 + 9 =
  27. 27.689 + 99 =
  28. 28.55 + 9 =
  29. 29.44 + 19 =
  30. 30.62 + 9 =
  31. 31.661 + 99 =
  32. 32.705 + 99 =
  33. 33.45 + 19 =
  34. 34.39 − 9 =
  35. 35.161 − 99 =
  36. 36.680 − 99 =
  37. 37.13 + 9 =
  38. 38.59 + 29 =
  39. 39.24 + 29 =
  40. 40.62 + 19 =

Answer key

  1. 6
  2. 899
  3. 26
  4. 75
  5. 58
  6. 23
  7. 18
  8. 71
  9. 108
  10. 45
  11. 44
  12. 71
  13. 57
  14. 89
  15. 103
  16. 36
  17. 61
  18. 52
  19. 37
  20. 12
  21. 41
  22. 38
  23. 217
  24. 554
  25. 55
  26. 38
  27. 788
  28. 64
  29. 63
  30. 71
  31. 760
  32. 804
  33. 64
  34. 30
  35. 62
  36. 581
  37. 22
  38. 88
  39. 53
  40. 81

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