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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 268 · 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. 1.35 − 29 =
  2. 2.40 + 29 =
  3. 3.26 − 9 =
  4. 4.28 − 19 =
  5. 5.53 + 9 =
  6. 6.47 − 19 =
  7. 7.83 − 29 =
  8. 8.79 − 19 =
  9. 9.733 − 99 =
  10. 10.65 − 29 =
  11. 11.260 + 99 =
  12. 12.74 + 29 =
  13. 13.24 + 9 =
  14. 14.70 + 19 =
  15. 15.22 − 19 =
  16. 16.93 − 29 =
  17. 17.56 + 19 =
  18. 18.23 − 19 =
  19. 19.58 − 19 =
  20. 20.22 + 9 =
  21. 21.646 − 99 =
  22. 22.161 + 99 =
  23. 23.42 − 9 =
  24. 24.25 + 19 =
  25. 25.102 − 29 =
  26. 26.180 + 99 =
  27. 27.27 − 19 =
  28. 28.39 + 19 =
  29. 29.77 − 29 =
  30. 30.69 + 19 =
  31. 31.34 + 9 =
  32. 32.716 + 99 =
  33. 33.243 − 99 =
  34. 34.41 − 29 =
  35. 35.58 + 29 =
  36. 36.75 + 19 =
  37. 37.28 + 19 =
  38. 38.255 − 99 =
  39. 39.19 + 9 =
  40. 40.54 + 19 =

Answer key

  1. 6
  2. 69
  3. 17
  4. 9
  5. 62
  6. 28
  7. 54
  8. 60
  9. 634
  10. 36
  11. 359
  12. 103
  13. 33
  14. 89
  15. 3
  16. 64
  17. 75
  18. 4
  19. 39
  20. 31
  21. 547
  22. 260
  23. 33
  24. 44
  25. 73
  26. 279
  27. 8
  28. 58
  29. 48
  30. 88
  31. 43
  32. 815
  33. 144
  34. 12
  35. 87
  36. 94
  37. 47
  38. 156
  39. 28
  40. 73

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