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Digit Sum Magic Worksheet

Maths tricks trick 10: Digit-sum magic · Set 979 · 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.Take 21 and take away the sum of its digits. What do you get?
  2. 2.Take 23 and take away the sum of its digits. What do you get?
  3. 3.5?90 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  4. 4.2?2 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  5. 5.?24 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  6. 6.7?34 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  7. 7.3?09 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  8. 8.?19 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  9. 9.Take 67 and take away the sum of its digits. What do you get?
  10. 10.?27 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  11. 11.600? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  12. 12.66?9 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  13. 13.155? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  14. 14.Take 97 and take away the sum of its digits. What do you get?
  15. 15.5?21 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  16. 16.5?25 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  17. 17.Take 73 and take away the sum of its digits. What do you get?
  18. 18.3?85 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  19. 19.?177 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  20. 20.?264 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  21. 21.?897 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  22. 22.Take 75 and take away the sum of its digits. What do you get?
  23. 23.87?0 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  24. 24.?022 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  25. 25.47?8 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  26. 26.14?0 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  27. 27.2?14 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  28. 28.86?0 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  29. 29.169? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  30. 30.Take 80 and take away the sum of its digits. What do you get?
  31. 31.Take 87 and take away the sum of its digits. What do you get?
  32. 32.4?24 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  33. 33.Take 24 and take away the sum of its digits. What do you get?
  34. 34.?482 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  35. 35.8?23 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  36. 36.1?73 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  37. 37.2?25 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  38. 38.459? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  39. 39.78?7 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  40. 40.Take 18 and take away the sum of its digits. What do you get?

Answer key

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

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