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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 308 · 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. 1.576 + 99 =
  2. 2.195 + 99 =
  3. 3.36 − 29 =
  4. 4.91 − 29 =
  5. 5.53 − 19 =
  6. 6.53 − 29 =
  7. 7.101 − 29 =
  8. 8.75 − 19 =
  9. 9.51 − 19 =
  10. 10.513 − 99 =
  11. 11.334 − 99 =
  12. 12.74 + 29 =
  13. 13.35 + 9 =
  14. 14.780 + 99 =
  15. 15.59 − 29 =
  16. 16.64 + 9 =
  17. 17.63 − 19 =
  18. 18.38 + 29 =
  19. 19.38 + 19 =
  20. 20.32 + 9 =
  21. 21.44 + 9 =
  22. 22.28 − 19 =
  23. 23.39 − 9 =
  24. 24.79 + 19 =
  25. 25.337 + 99 =
  26. 26.781 − 99 =
  27. 27.58 + 29 =
  28. 28.23 + 19 =
  29. 29.48 + 9 =
  30. 30.40 − 9 =
  31. 31.75 + 29 =
  32. 32.25 − 19 =
  33. 33.626 + 99 =
  34. 34.771 + 99 =
  35. 35.58 + 19 =
  36. 36.70 + 19 =
  37. 37.203 − 99 =
  38. 38.40 + 19 =
  39. 39.87 − 29 =
  40. 40.73 + 9 =

Answer key

  1. 675
  2. 294
  3. 7
  4. 62
  5. 34
  6. 24
  7. 72
  8. 56
  9. 32
  10. 414
  11. 235
  12. 103
  13. 44
  14. 879
  15. 30
  16. 73
  17. 44
  18. 67
  19. 57
  20. 41
  21. 53
  22. 9
  23. 30
  24. 98
  25. 436
  26. 682
  27. 87
  28. 42
  29. 57
  30. 31
  31. 104
  32. 6
  33. 725
  34. 870
  35. 77
  36. 89
  37. 104
  38. 59
  39. 58
  40. 82

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