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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 916 · 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. 1.408 + 99 =
  2. 2.529 + 99 =
  3. 3.353 − 99 =
  4. 4.43 − 9 =
  5. 5.28 + 19 =
  6. 6.57 − 9 =
  7. 7.32 − 29 =
  8. 8.182 − 99 =
  9. 9.42 + 19 =
  10. 10.17 − 9 =
  11. 11.23 + 9 =
  12. 12.286 − 99 =
  13. 13.13 + 19 =
  14. 14.31 + 9 =
  15. 15.618 + 99 =
  16. 16.85 − 19 =
  17. 17.87 − 9 =
  18. 18.222 + 99 =
  19. 19.47 − 29 =
  20. 20.174 − 99 =
  21. 21.39 + 19 =
  22. 22.90 − 19 =
  23. 23.55 + 29 =
  24. 24.554 + 99 =
  25. 25.45 + 9 =
  26. 26.77 + 29 =
  27. 27.46 + 29 =
  28. 28.39 − 29 =
  29. 29.54 + 29 =
  30. 30.247 − 99 =
  31. 31.79 + 29 =
  32. 32.31 − 9 =
  33. 33.217 + 99 =
  34. 34.66 − 29 =
  35. 35.81 − 19 =
  36. 36.80 + 9 =
  37. 37.15 + 19 =
  38. 38.22 + 9 =
  39. 39.89 − 9 =
  40. 40.65 + 9 =

Answer key

  1. 507
  2. 628
  3. 254
  4. 34
  5. 47
  6. 48
  7. 3
  8. 83
  9. 61
  10. 8
  11. 32
  12. 187
  13. 32
  14. 40
  15. 717
  16. 66
  17. 78
  18. 321
  19. 18
  20. 75
  21. 58
  22. 71
  23. 84
  24. 653
  25. 54
  26. 106
  27. 75
  28. 10
  29. 83
  30. 148
  31. 108
  32. 22
  33. 316
  34. 37
  35. 62
  36. 89
  37. 34
  38. 31
  39. 80
  40. 74

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