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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 817 · 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. 1.39 + 9 =
  2. 2.24 − 9 =
  3. 3.140 + 99 =
  4. 4.37 + 29 =
  5. 5.66 + 9 =
  6. 6.65 − 19 =
  7. 7.72 + 9 =
  8. 8.46 − 19 =
  9. 9.14 + 29 =
  10. 10.66 − 29 =
  11. 11.43 + 19 =
  12. 12.90 − 19 =
  13. 13.25 + 9 =
  14. 14.157 − 99 =
  15. 15.14 + 19 =
  16. 16.89 − 29 =
  17. 17.735 + 99 =
  18. 18.70 + 29 =
  19. 19.658 − 99 =
  20. 20.771 + 99 =
  21. 21.61 + 9 =
  22. 22.70 + 9 =
  23. 23.75 + 9 =
  24. 24.29 − 9 =
  25. 25.22 − 19 =
  26. 26.29 + 19 =
  27. 27.201 − 99 =
  28. 28.255 + 99 =
  29. 29.69 + 9 =
  30. 30.49 − 29 =
  31. 31.32 − 19 =
  32. 32.67 + 9 =
  33. 33.18 + 19 =
  34. 34.60 − 29 =
  35. 35.34 − 19 =
  36. 36.319 + 99 =
  37. 37.682 + 99 =
  38. 38.60 + 9 =
  39. 39.70 − 29 =
  40. 40.74 + 29 =

Answer key

  1. 48
  2. 15
  3. 239
  4. 66
  5. 75
  6. 46
  7. 81
  8. 27
  9. 43
  10. 37
  11. 62
  12. 71
  13. 34
  14. 58
  15. 33
  16. 60
  17. 834
  18. 99
  19. 559
  20. 870
  21. 70
  22. 79
  23. 84
  24. 20
  25. 3
  26. 48
  27. 102
  28. 354
  29. 78
  30. 20
  31. 13
  32. 76
  33. 37
  34. 31
  35. 15
  36. 418
  37. 781
  38. 69
  39. 41
  40. 103

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