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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 692 · 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. 1.86 − 9 =
  2. 2.98 − 19 =
  3. 3.21 − 9 =
  4. 4.81 − 29 =
  5. 5.45 − 9 =
  6. 6.74 − 9 =
  7. 7.637 + 99 =
  8. 8.16 − 9 =
  9. 9.53 + 9 =
  10. 10.72 − 19 =
  11. 11.76 − 19 =
  12. 12.34 − 19 =
  13. 13.93 − 29 =
  14. 14.67 + 9 =
  15. 15.330 − 99 =
  16. 16.387 + 99 =
  17. 17.808 − 99 =
  18. 18.51 − 19 =
  19. 19.31 + 9 =
  20. 20.43 + 9 =
  21. 21.65 + 29 =
  22. 22.92 − 29 =
  23. 23.49 + 9 =
  24. 24.31 − 9 =
  25. 25.65 − 19 =
  26. 26.78 − 9 =
  27. 27.66 − 9 =
  28. 28.74 + 29 =
  29. 29.789 + 99 =
  30. 30.52 − 9 =
  31. 31.33 − 9 =
  32. 32.42 − 29 =
  33. 33.12 − 9 =
  34. 34.83 − 29 =
  35. 35.371 − 99 =
  36. 36.70 + 9 =
  37. 37.37 + 29 =
  38. 38.57 − 19 =
  39. 39.862 − 99 =
  40. 40.38 + 9 =

Answer key

  1. 77
  2. 79
  3. 12
  4. 52
  5. 36
  6. 65
  7. 736
  8. 7
  9. 62
  10. 53
  11. 57
  12. 15
  13. 64
  14. 76
  15. 231
  16. 486
  17. 709
  18. 32
  19. 40
  20. 52
  21. 94
  22. 63
  23. 58
  24. 22
  25. 46
  26. 69
  27. 57
  28. 103
  29. 888
  30. 43
  31. 24
  32. 13
  33. 3
  34. 54
  35. 272
  36. 79
  37. 66
  38. 38
  39. 763
  40. 47

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