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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 975 · 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. 1.50 + 19 =
  2. 2.730 + 99 =
  3. 3.310 + 99 =
  4. 4.35 + 29 =
  5. 5.79 − 9 =
  6. 6.663 + 99 =
  7. 7.85 − 19 =
  8. 8.53 + 19 =
  9. 9.839 − 99 =
  10. 10.366 − 99 =
  11. 11.65 − 9 =
  12. 12.66 + 29 =
  13. 13.41 + 9 =
  14. 14.559 − 99 =
  15. 15.60 − 9 =
  16. 16.48 + 9 =
  17. 17.38 − 29 =
  18. 18.58 − 9 =
  19. 19.105 − 29 =
  20. 20.57 + 29 =
  21. 21.54 − 19 =
  22. 22.16 − 9 =
  23. 23.341 + 99 =
  24. 24.73 + 19 =
  25. 25.59 + 19 =
  26. 26.72 − 19 =
  27. 27.71 − 29 =
  28. 28.15 + 19 =
  29. 29.29 + 9 =
  30. 30.42 − 29 =
  31. 31.75 − 19 =
  32. 32.50 − 9 =
  33. 33.78 + 19 =
  34. 34.226 + 99 =
  35. 35.54 + 29 =
  36. 36.94 − 29 =
  37. 37.56 + 29 =
  38. 38.249 − 99 =
  39. 39.24 + 19 =
  40. 40.25 + 9 =

Answer key

  1. 69
  2. 829
  3. 409
  4. 64
  5. 70
  6. 762
  7. 66
  8. 72
  9. 740
  10. 267
  11. 56
  12. 95
  13. 50
  14. 460
  15. 51
  16. 57
  17. 9
  18. 49
  19. 76
  20. 86
  21. 35
  22. 7
  23. 440
  24. 92
  25. 78
  26. 53
  27. 42
  28. 34
  29. 38
  30. 13
  31. 56
  32. 41
  33. 97
  34. 325
  35. 83
  36. 65
  37. 85
  38. 150
  39. 43
  40. 34

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