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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 779 · 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. 1.40 − 9 =
  2. 2.35 + 9 =
  3. 3.71 + 19 =
  4. 4.844 − 99 =
  5. 5.412 − 99 =
  6. 6.259 − 99 =
  7. 7.154 + 99 =
  8. 8.583 − 99 =
  9. 9.403 + 99 =
  10. 10.28 − 9 =
  11. 11.16 + 9 =
  12. 12.22 + 29 =
  13. 13.324 − 99 =
  14. 14.53 + 19 =
  15. 15.79 + 19 =
  16. 16.51 − 29 =
  17. 17.22 − 9 =
  18. 18.62 + 29 =
  19. 19.697 + 99 =
  20. 20.77 − 29 =
  21. 21.76 + 9 =
  22. 22.604 − 99 =
  23. 23.48 + 19 =
  24. 24.54 − 29 =
  25. 25.97 − 29 =
  26. 26.56 + 19 =
  27. 27.38 − 9 =
  28. 28.536 + 99 =
  29. 29.66 − 9 =
  30. 30.68 + 19 =
  31. 31.93 − 19 =
  32. 32.35 − 9 =
  33. 33.896 − 99 =
  34. 34.16 − 9 =
  35. 35.28 + 19 =
  36. 36.19 + 29 =
  37. 37.43 − 19 =
  38. 38.249 + 99 =
  39. 39.72 + 29 =
  40. 40.23 − 9 =

Answer key

  1. 31
  2. 44
  3. 90
  4. 745
  5. 313
  6. 160
  7. 253
  8. 484
  9. 502
  10. 19
  11. 25
  12. 51
  13. 225
  14. 72
  15. 98
  16. 22
  17. 13
  18. 91
  19. 796
  20. 48
  21. 85
  22. 505
  23. 67
  24. 25
  25. 68
  26. 75
  27. 29
  28. 635
  29. 57
  30. 87
  31. 74
  32. 26
  33. 797
  34. 7
  35. 47
  36. 48
  37. 24
  38. 348
  39. 101
  40. 14

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