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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 696 · 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. 1.562 + 99 =
  2. 2.519 − 99 =
  3. 3.89 − 19 =
  4. 4.73 − 9 =
  5. 5.75 + 29 =
  6. 6.31 + 9 =
  7. 7.21 + 19 =
  8. 8.24 + 9 =
  9. 9.32 + 19 =
  10. 10.46 − 29 =
  11. 11.44 + 19 =
  12. 12.763 − 99 =
  13. 13.60 + 19 =
  14. 14.244 − 99 =
  15. 15.36 − 29 =
  16. 16.83 − 29 =
  17. 17.78 + 29 =
  18. 18.62 + 29 =
  19. 19.48 − 19 =
  20. 20.30 − 9 =
  21. 21.221 − 99 =
  22. 22.14 + 9 =
  23. 23.22 − 9 =
  24. 24.749 + 99 =
  25. 25.53 − 19 =
  26. 26.74 + 29 =
  27. 27.52 + 19 =
  28. 28.57 − 9 =
  29. 29.15 + 9 =
  30. 30.24 + 29 =
  31. 31.34 + 19 =
  32. 32.879 − 99 =
  33. 33.78 − 19 =
  34. 34.31 − 9 =
  35. 35.44 − 19 =
  36. 36.74 − 9 =
  37. 37.45 − 9 =
  38. 38.88 − 19 =
  39. 39.48 + 19 =
  40. 40.67 − 19 =

Answer key

  1. 661
  2. 420
  3. 70
  4. 64
  5. 104
  6. 40
  7. 40
  8. 33
  9. 51
  10. 17
  11. 63
  12. 664
  13. 79
  14. 145
  15. 7
  16. 54
  17. 107
  18. 91
  19. 29
  20. 21
  21. 122
  22. 23
  23. 13
  24. 848
  25. 34
  26. 103
  27. 71
  28. 48
  29. 24
  30. 53
  31. 53
  32. 780
  33. 59
  34. 22
  35. 25
  36. 65
  37. 36
  38. 69
  39. 67
  40. 48

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