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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 986 · 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. 1.892 − 99 =
  2. 2.86 − 9 =
  3. 3.83 − 19 =
  4. 4.21 + 19 =
  5. 5.85 − 9 =
  6. 6.111 + 99 =
  7. 7.79 − 9 =
  8. 8.49 − 29 =
  9. 9.72 + 19 =
  10. 10.25 + 9 =
  11. 11.23 + 19 =
  12. 12.523 − 99 =
  13. 13.40 + 19 =
  14. 14.64 + 19 =
  15. 15.24 − 9 =
  16. 16.40 − 19 =
  17. 17.75 − 19 =
  18. 18.49 − 9 =
  19. 19.824 − 99 =
  20. 20.320 + 99 =
  21. 21.643 + 99 =
  22. 22.44 + 9 =
  23. 23.12 + 19 =
  24. 24.57 − 29 =
  25. 25.68 + 19 =
  26. 26.28 + 19 =
  27. 27.18 + 9 =
  28. 28.789 − 99 =
  29. 29.57 + 9 =
  30. 30.64 − 19 =
  31. 31.314 − 99 =
  32. 32.26 + 29 =
  33. 33.79 + 19 =
  34. 34.103 − 29 =
  35. 35.83 − 9 =
  36. 36.401 − 99 =
  37. 37.84 − 29 =
  38. 38.22 + 19 =
  39. 39.73 − 29 =
  40. 40.19 + 29 =

Answer key

  1. 793
  2. 77
  3. 64
  4. 40
  5. 76
  6. 210
  7. 70
  8. 20
  9. 91
  10. 34
  11. 42
  12. 424
  13. 59
  14. 83
  15. 15
  16. 21
  17. 56
  18. 40
  19. 725
  20. 419
  21. 742
  22. 53
  23. 31
  24. 28
  25. 87
  26. 47
  27. 27
  28. 690
  29. 66
  30. 45
  31. 215
  32. 55
  33. 98
  34. 74
  35. 74
  36. 302
  37. 55
  38. 41
  39. 44
  40. 48

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