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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 625 · 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. 1.18 + 29 =
  2. 2.33 + 9 =
  3. 3.451 − 99 =
  4. 4.583 + 99 =
  5. 5.57 − 19 =
  6. 6.37 − 9 =
  7. 7.18 − 9 =
  8. 8.882 − 99 =
  9. 9.407 + 99 =
  10. 10.224 + 99 =
  11. 11.103 − 29 =
  12. 12.86 − 19 =
  13. 13.768 + 99 =
  14. 14.95 − 19 =
  15. 15.13 + 29 =
  16. 16.39 + 19 =
  17. 17.43 + 19 =
  18. 18.27 − 9 =
  19. 19.21 + 19 =
  20. 20.18 + 19 =
  21. 21.24 + 9 =
  22. 22.24 − 9 =
  23. 23.876 − 99 =
  24. 24.507 + 99 =
  25. 25.66 + 29 =
  26. 26.179 + 99 =
  27. 27.671 + 99 =
  28. 28.808 − 99 =
  29. 29.105 − 29 =
  30. 30.38 − 29 =
  31. 31.53 − 9 =
  32. 32.32 − 19 =
  33. 33.526 − 99 =
  34. 34.26 + 29 =
  35. 35.858 − 99 =
  36. 36.14 − 9 =
  37. 37.455 + 99 =
  38. 38.211 + 99 =
  39. 39.75 − 9 =
  40. 40.66 − 19 =

Answer key

  1. 47
  2. 42
  3. 352
  4. 682
  5. 38
  6. 28
  7. 9
  8. 783
  9. 506
  10. 323
  11. 74
  12. 67
  13. 867
  14. 76
  15. 42
  16. 58
  17. 62
  18. 18
  19. 40
  20. 37
  21. 33
  22. 15
  23. 777
  24. 606
  25. 95
  26. 278
  27. 770
  28. 709
  29. 76
  30. 9
  31. 44
  32. 13
  33. 427
  34. 55
  35. 759
  36. 5
  37. 554
  38. 310
  39. 66
  40. 47

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