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Digit Sum Magic Worksheet

Maths tricks trick 10: Digit-sum magic · Set 447 · 40 questions
TalentJR

The trick (Digits add to the 9 table): Add the digits you can see. Find the next number in the 9 table (9, 18, 27 …) above that total. The hidden digit is the difference. (Any number minus its digit sum is in the 9 table too.)

NameDateTime takenScore ___ / 40
  1. 1.21? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  2. 2.Take 15 and take away the sum of its digits. What do you get?
  3. 3.5?2 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  4. 4.11?8 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  5. 5.29?3 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  6. 6.Take 70 and take away the sum of its digits. What do you get?
  7. 7.Take 80 and take away the sum of its digits. What do you get?
  8. 8.Take 18 and take away the sum of its digits. What do you get?
  9. 9.?659 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  10. 10.Take 77 and take away the sum of its digits. What do you get?
  11. 11.?723 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  12. 12.?00 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  13. 13.1?69 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  14. 14.15? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  15. 15.27? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  16. 16.?196 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  17. 17.161? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  18. 18.863? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  19. 19.?649 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  20. 20.?67 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  21. 21.Take 71 and take away the sum of its digits. What do you get?
  22. 22.?385 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  23. 23.Take 24 and take away the sum of its digits. What do you get?
  24. 24.?400 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  25. 25.?460 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  26. 26.Take 17 and take away the sum of its digits. What do you get?
  27. 27.Take 91 and take away the sum of its digits. What do you get?
  28. 28.332? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  29. 29.Take 61 and take away the sum of its digits. What do you get?
  30. 30.4?8 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  31. 31.808? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  32. 32.29?4 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  33. 33.?088 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  34. 34.40?9 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  35. 35.286? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  36. 36.Take 28 and take away the sum of its digits. What do you get?
  37. 37.?991 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  38. 38.691? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  39. 39.3?90 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  40. 40.8?78 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?

Answer key

  1. 6
  2. 9
  3. 2
  4. 8
  5. 4
  6. 63
  7. 72
  8. 9
  9. 7
  10. 63
  11. 6
  12. 9
  13. 2
  14. 3
  15. 9
  16. 2
  17. 1
  18. 1
  19. 8
  20. 5
  21. 63
  22. 2
  23. 18
  24. 5
  25. 8
  26. 9
  27. 81
  28. 1
  29. 54
  30. 6
  31. 2
  32. 3
  33. 2
  34. 5
  35. 2
  36. 18
  37. 8
  38. 2
  39. 6
  40. 4

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