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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 576 · 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. 1.74 − 29 =
  2. 2.85 − 9 =
  3. 3.30 − 9 =
  4. 4.67 + 9 =
  5. 5.69 + 19 =
  6. 6.27 + 9 =
  7. 7.54 − 29 =
  8. 8.75 + 29 =
  9. 9.70 − 19 =
  10. 10.57 + 9 =
  11. 11.80 + 9 =
  12. 12.60 + 9 =
  13. 13.29 − 9 =
  14. 14.23 − 19 =
  15. 15.583 + 99 =
  16. 16.37 + 19 =
  17. 17.22 + 19 =
  18. 18.560 − 99 =
  19. 19.31 + 29 =
  20. 20.66 + 9 =
  21. 21.37 + 9 =
  22. 22.21 + 29 =
  23. 23.56 + 19 =
  24. 24.64 + 29 =
  25. 25.49 + 29 =
  26. 26.35 + 29 =
  27. 27.775 − 99 =
  28. 28.168 + 99 =
  29. 29.98 − 29 =
  30. 30.70 − 9 =
  31. 31.52 + 9 =
  32. 32.64 + 9 =
  33. 33.24 + 29 =
  34. 34.745 − 99 =
  35. 35.43 + 29 =
  36. 36.81 − 29 =
  37. 37.465 − 99 =
  38. 38.19 − 9 =
  39. 39.158 − 99 =
  40. 40.25 − 9 =

Answer key

  1. 45
  2. 76
  3. 21
  4. 76
  5. 88
  6. 36
  7. 25
  8. 104
  9. 51
  10. 66
  11. 89
  12. 69
  13. 20
  14. 4
  15. 682
  16. 56
  17. 41
  18. 461
  19. 60
  20. 75
  21. 46
  22. 50
  23. 75
  24. 93
  25. 78
  26. 64
  27. 676
  28. 267
  29. 69
  30. 61
  31. 61
  32. 73
  33. 53
  34. 646
  35. 72
  36. 52
  37. 366
  38. 10
  39. 59
  40. 16

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