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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 979 · 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. 1.76 + 9 =
  2. 2.98 − 19 =
  3. 3.38 + 29 =
  4. 4.17 + 9 =
  5. 5.97 − 19 =
  6. 6.40 + 9 =
  7. 7.28 + 9 =
  8. 8.75 + 9 =
  9. 9.615 + 99 =
  10. 10.428 − 99 =
  11. 11.25 − 19 =
  12. 12.85 − 9 =
  13. 13.72 − 19 =
  14. 14.44 − 29 =
  15. 15.82 − 29 =
  16. 16.60 + 9 =
  17. 17.69 − 29 =
  18. 18.42 − 9 =
  19. 19.46 + 9 =
  20. 20.78 − 9 =
  21. 21.36 − 19 =
  22. 22.25 + 9 =
  23. 23.31 + 9 =
  24. 24.48 − 19 =
  25. 25.44 + 9 =
  26. 26.67 + 19 =
  27. 27.527 − 99 =
  28. 28.393 − 99 =
  29. 29.73 + 29 =
  30. 30.844 − 99 =
  31. 31.43 + 9 =
  32. 32.39 − 19 =
  33. 33.267 − 99 =
  34. 34.148 + 99 =
  35. 35.80 − 29 =
  36. 36.26 − 19 =
  37. 37.408 + 99 =
  38. 38.187 − 99 =
  39. 39.105 − 29 =
  40. 40.69 − 9 =

Answer key

  1. 85
  2. 79
  3. 67
  4. 26
  5. 78
  6. 49
  7. 37
  8. 84
  9. 714
  10. 329
  11. 6
  12. 76
  13. 53
  14. 15
  15. 53
  16. 69
  17. 40
  18. 33
  19. 55
  20. 69
  21. 17
  22. 34
  23. 40
  24. 29
  25. 53
  26. 86
  27. 428
  28. 294
  29. 102
  30. 745
  31. 52
  32. 20
  33. 168
  34. 247
  35. 51
  36. 7
  37. 507
  38. 88
  39. 76
  40. 60

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