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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 162 · 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. 1.159 − 99 =
  2. 2.36 − 29 =
  3. 3.353 + 99 =
  4. 4.56 + 19 =
  5. 5.80 − 29 =
  6. 6.57 + 29 =
  7. 7.547 − 99 =
  8. 8.38 + 29 =
  9. 9.33 + 29 =
  10. 10.403 + 99 =
  11. 11.100 − 29 =
  12. 12.351 + 99 =
  13. 13.61 + 19 =
  14. 14.66 + 9 =
  15. 15.60 + 19 =
  16. 16.84 − 19 =
  17. 17.20 − 9 =
  18. 18.212 − 99 =
  19. 19.22 − 19 =
  20. 20.684 + 99 =
  21. 21.21 − 9 =
  22. 22.51 + 9 =
  23. 23.58 − 9 =
  24. 24.485 − 99 =
  25. 25.287 − 99 =
  26. 26.43 − 19 =
  27. 27.177 + 99 =
  28. 28.86 − 9 =
  29. 29.60 + 9 =
  30. 30.169 − 99 =
  31. 31.43 + 19 =
  32. 32.33 + 9 =
  33. 33.84 − 29 =
  34. 34.47 + 9 =
  35. 35.99 − 29 =
  36. 36.62 − 29 =
  37. 37.59 − 9 =
  38. 38.674 + 99 =
  39. 39.829 − 99 =
  40. 40.48 − 29 =

Answer key

  1. 60
  2. 7
  3. 452
  4. 75
  5. 51
  6. 86
  7. 448
  8. 67
  9. 62
  10. 502
  11. 71
  12. 450
  13. 80
  14. 75
  15. 79
  16. 65
  17. 11
  18. 113
  19. 3
  20. 783
  21. 12
  22. 60
  23. 49
  24. 386
  25. 188
  26. 24
  27. 276
  28. 77
  29. 69
  30. 70
  31. 62
  32. 42
  33. 55
  34. 56
  35. 70
  36. 33
  37. 50
  38. 773
  39. 730
  40. 19

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