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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 70 · 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. 1.14 − 9 =
  2. 2.18 + 29 =
  3. 3.62 + 9 =
  4. 4.887 − 99 =
  5. 5.34 + 9 =
  6. 6.494 + 99 =
  7. 7.39 + 29 =
  8. 8.652 + 99 =
  9. 9.67 − 9 =
  10. 10.603 − 99 =
  11. 11.33 + 29 =
  12. 12.32 − 9 =
  13. 13.72 + 19 =
  14. 14.532 − 99 =
  15. 15.12 − 9 =
  16. 16.62 − 29 =
  17. 17.60 − 29 =
  18. 18.866 − 99 =
  19. 19.25 − 9 =
  20. 20.49 − 29 =
  21. 21.333 + 99 =
  22. 22.68 − 9 =
  23. 23.259 − 99 =
  24. 24.59 − 19 =
  25. 25.18 − 9 =
  26. 26.71 + 9 =
  27. 27.54 + 9 =
  28. 28.41 + 9 =
  29. 29.547 + 99 =
  30. 30.74 + 19 =
  31. 31.78 + 29 =
  32. 32.57 − 9 =
  33. 33.71 − 9 =
  34. 34.497 − 99 =
  35. 35.34 + 29 =
  36. 36.21 − 9 =
  37. 37.364 + 99 =
  38. 38.25 + 29 =
  39. 39.46 + 9 =
  40. 40.86 − 29 =

Answer key

  1. 5
  2. 47
  3. 71
  4. 788
  5. 43
  6. 593
  7. 68
  8. 751
  9. 58
  10. 504
  11. 62
  12. 23
  13. 91
  14. 433
  15. 3
  16. 33
  17. 31
  18. 767
  19. 16
  20. 20
  21. 432
  22. 59
  23. 160
  24. 40
  25. 9
  26. 80
  27. 63
  28. 50
  29. 646
  30. 93
  31. 107
  32. 48
  33. 62
  34. 398
  35. 63
  36. 12
  37. 463
  38. 54
  39. 55
  40. 57

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