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Digit Sum Magic Worksheet

Maths tricks trick 10: Digit-sum magic · Set 990 · 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 80 and take away the sum of its digits. What do you get?
  2. 2.Take 73 and take away the sum of its digits. What do you get?
  3. 3.?777 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  4. 4.Take 96 and take away the sum of its digits. What do you get?
  5. 5.Take 99 and take away the sum of its digits. What do you get?
  6. 6.Take 93 and take away the sum of its digits. What do you get?
  7. 7.7?92 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  8. 8.Take 12 and take away the sum of its digits. What do you get?
  9. 9.Take 34 and take away the sum of its digits. What do you get?
  10. 10.659? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  11. 11.?192 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  12. 12.?244 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  13. 13.363? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  14. 14.162? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  15. 15.Take 22 and take away the sum of its digits. What do you get?
  16. 16.Take 41 and take away the sum of its digits. What do you get?
  17. 17.436? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  18. 18.8?11 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  19. 19.?364 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  20. 20.Take 47 and take away the sum of its digits. What do you get?
  21. 21.491? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  22. 22.Take 71 and take away the sum of its digits. What do you get?
  23. 23.?56 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  24. 24.Take 81 and take away the sum of its digits. What do you get?
  25. 25.60?3 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  26. 26.3?79 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  27. 27.68?2 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  28. 28.Take 32 and take away the sum of its digits. What do you get?
  29. 29.4?0 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  30. 30.Take 86 and take away the sum of its digits. What do you get?
  31. 31.86?2 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  32. 32.Take 16 and take away the sum of its digits. What do you get?
  33. 33.138? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  34. 34.2?12 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  35. 35.Take 50 and take away the sum of its digits. What do you get?
  36. 36.7?18 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  37. 37.Take 78 and take away the sum of its digits. What do you get?
  38. 38.8?68 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  39. 39.Take 62 and take away the sum of its digits. What do you get?
  40. 40.276? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?

Answer key

  1. 72
  2. 63
  3. 6
  4. 81
  5. 81
  6. 81
  7. 9
  8. 9
  9. 27
  10. 7
  11. 6
  12. 8
  13. 6
  14. 9
  15. 18
  16. 36
  17. 5
  18. 8
  19. 5
  20. 36
  21. 4
  22. 63
  23. 7
  24. 72
  25. 9
  26. 8
  27. 2
  28. 27
  29. 5
  30. 72
  31. 2
  32. 9
  33. 6
  34. 4
  35. 45
  36. 2
  37. 63
  38. 5
  39. 54
  40. 3

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