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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 241 · 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. 1.69 − 29 =
  2. 2.66 + 29 =
  3. 3.40 − 19 =
  4. 4.58 − 9 =
  5. 5.51 + 29 =
  6. 6.13 + 9 =
  7. 7.55 + 29 =
  8. 8.68 − 19 =
  9. 9.73 − 9 =
  10. 10.60 + 29 =
  11. 11.23 + 19 =
  12. 12.71 + 29 =
  13. 13.619 + 99 =
  14. 14.77 + 9 =
  15. 15.18 + 9 =
  16. 16.24 − 9 =
  17. 17.32 − 29 =
  18. 18.220 + 99 =
  19. 19.46 + 9 =
  20. 20.662 − 99 =
  21. 21.64 − 29 =
  22. 22.888 − 99 =
  23. 23.544 + 99 =
  24. 24.105 − 29 =
  25. 25.542 + 99 =
  26. 26.62 + 9 =
  27. 27.32 − 9 =
  28. 28.423 − 99 =
  29. 29.212 + 99 =
  30. 30.31 + 29 =
  31. 31.81 − 19 =
  32. 32.81 − 9 =
  33. 33.78 + 29 =
  34. 34.30 + 19 =
  35. 35.41 + 19 =
  36. 36.363 + 99 =
  37. 37.42 + 9 =
  38. 38.52 + 29 =
  39. 39.855 − 99 =
  40. 40.12 + 9 =

Answer key

  1. 40
  2. 95
  3. 21
  4. 49
  5. 80
  6. 22
  7. 84
  8. 49
  9. 64
  10. 89
  11. 42
  12. 100
  13. 718
  14. 86
  15. 27
  16. 15
  17. 3
  18. 319
  19. 55
  20. 563
  21. 35
  22. 789
  23. 643
  24. 76
  25. 641
  26. 71
  27. 23
  28. 324
  29. 311
  30. 60
  31. 62
  32. 72
  33. 107
  34. 49
  35. 60
  36. 462
  37. 51
  38. 81
  39. 756
  40. 21

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