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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 646 · 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. 1.80 + 19 =
  2. 2.26 + 19 =
  3. 3.37 − 29 =
  4. 4.49 + 19 =
  5. 5.25 − 9 =
  6. 6.78 − 29 =
  7. 7.27 − 19 =
  8. 8.84 − 9 =
  9. 9.61 + 19 =
  10. 10.38 + 9 =
  11. 11.427 − 99 =
  12. 12.184 + 99 =
  13. 13.39 + 29 =
  14. 14.70 + 9 =
  15. 15.266 − 99 =
  16. 16.31 + 9 =
  17. 17.97 − 29 =
  18. 18.60 + 9 =
  19. 19.77 + 9 =
  20. 20.87 − 29 =
  21. 21.30 − 9 =
  22. 22.25 + 9 =
  23. 23.60 + 29 =
  24. 24.27 + 9 =
  25. 25.337 + 99 =
  26. 26.13 + 19 =
  27. 27.68 + 29 =
  28. 28.44 − 9 =
  29. 29.32 − 9 =
  30. 30.39 − 9 =
  31. 31.67 + 29 =
  32. 32.31 + 19 =
  33. 33.54 − 29 =
  34. 34.31 − 9 =
  35. 35.82 − 9 =
  36. 36.78 − 9 =
  37. 37.673 + 99 =
  38. 38.747 − 99 =
  39. 39.76 − 19 =
  40. 40.55 − 9 =

Answer key

  1. 99
  2. 45
  3. 8
  4. 68
  5. 16
  6. 49
  7. 8
  8. 75
  9. 80
  10. 47
  11. 328
  12. 283
  13. 68
  14. 79
  15. 167
  16. 40
  17. 68
  18. 69
  19. 86
  20. 58
  21. 21
  22. 34
  23. 89
  24. 36
  25. 436
  26. 32
  27. 97
  28. 35
  29. 23
  30. 30
  31. 96
  32. 50
  33. 25
  34. 22
  35. 73
  36. 69
  37. 772
  38. 648
  39. 57
  40. 46

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