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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 633 · 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. 1.599 + 99 =
  2. 2.605 + 99 =
  3. 3.87 − 19 =
  4. 4.32 + 19 =
  5. 5.241 + 99 =
  6. 6.334 − 99 =
  7. 7.38 − 29 =
  8. 8.78 − 19 =
  9. 9.55 − 29 =
  10. 10.107 − 29 =
  11. 11.261 + 99 =
  12. 12.70 − 9 =
  13. 13.882 − 99 =
  14. 14.17 + 19 =
  15. 15.797 − 99 =
  16. 16.26 + 29 =
  17. 17.748 − 99 =
  18. 18.108 + 99 =
  19. 19.226 − 99 =
  20. 20.738 − 99 =
  21. 21.82 − 19 =
  22. 22.34 − 9 =
  23. 23.26 + 9 =
  24. 24.30 + 9 =
  25. 25.52 + 19 =
  26. 26.44 + 9 =
  27. 27.26 + 19 =
  28. 28.16 + 9 =
  29. 29.37 + 29 =
  30. 30.527 + 99 =
  31. 31.76 + 19 =
  32. 32.83 − 9 =
  33. 33.180 + 99 =
  34. 34.508 − 99 =
  35. 35.96 − 19 =
  36. 36.766 − 99 =
  37. 37.516 + 99 =
  38. 38.28 − 9 =
  39. 39.159 + 99 =
  40. 40.46 + 19 =

Answer key

  1. 698
  2. 704
  3. 68
  4. 51
  5. 340
  6. 235
  7. 9
  8. 59
  9. 26
  10. 78
  11. 360
  12. 61
  13. 783
  14. 36
  15. 698
  16. 55
  17. 649
  18. 207
  19. 127
  20. 639
  21. 63
  22. 25
  23. 35
  24. 39
  25. 71
  26. 53
  27. 45
  28. 25
  29. 66
  30. 626
  31. 95
  32. 74
  33. 279
  34. 409
  35. 77
  36. 667
  37. 615
  38. 19
  39. 258
  40. 65

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