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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 557 · 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. 1.79 − 9 =
  2. 2.93 − 29 =
  3. 3.325 − 99 =
  4. 4.56 + 19 =
  5. 5.76 − 9 =
  6. 6.25 − 9 =
  7. 7.30 − 19 =
  8. 8.46 − 29 =
  9. 9.49 + 19 =
  10. 10.303 + 99 =
  11. 11.94 − 19 =
  12. 12.32 − 29 =
  13. 13.29 − 9 =
  14. 14.44 − 29 =
  15. 15.66 + 19 =
  16. 16.75 + 29 =
  17. 17.36 + 9 =
  18. 18.157 + 99 =
  19. 19.37 + 19 =
  20. 20.330 − 99 =
  21. 21.71 + 29 =
  22. 22.80 + 29 =
  23. 23.48 − 29 =
  24. 24.35 − 29 =
  25. 25.40 + 9 =
  26. 26.47 + 9 =
  27. 27.32 − 9 =
  28. 28.72 − 19 =
  29. 29.836 − 99 =
  30. 30.589 + 99 =
  31. 31.13 − 9 =
  32. 32.16 + 19 =
  33. 33.55 − 19 =
  34. 34.77 + 9 =
  35. 35.22 + 19 =
  36. 36.63 − 19 =
  37. 37.51 − 29 =
  38. 38.544 − 99 =
  39. 39.85 − 9 =
  40. 40.100 − 29 =

Answer key

  1. 70
  2. 64
  3. 226
  4. 75
  5. 67
  6. 16
  7. 11
  8. 17
  9. 68
  10. 402
  11. 75
  12. 3
  13. 20
  14. 15
  15. 85
  16. 104
  17. 45
  18. 256
  19. 56
  20. 231
  21. 100
  22. 109
  23. 19
  24. 6
  25. 49
  26. 56
  27. 23
  28. 53
  29. 737
  30. 688
  31. 4
  32. 35
  33. 36
  34. 86
  35. 41
  36. 44
  37. 22
  38. 445
  39. 76
  40. 71

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