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Digit Sum Magic Worksheet

Maths tricks trick 10: Digit-sum magic · Set 647 · 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. 1.280? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  2. 2.Take 71 and take away the sum of its digits. What do you get?
  3. 3.Take 12 and take away the sum of its digits. What do you get?
  4. 4.81?3 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  5. 5.20?8 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  6. 6.5?14 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  7. 7.?392 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  8. 8.209? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  9. 9.77?5 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  10. 10.306? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  11. 11.7?7 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  12. 12.24?7 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  13. 13.76?4 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  14. 14.?90 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  15. 15.1?7 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  16. 16.7?0 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  17. 17.Take 90 and take away the sum of its digits. What do you get?
  18. 18.Take 85 and take away the sum of its digits. What do you get?
  19. 19.Take 21 and take away the sum of its digits. What do you get?
  20. 20.?676 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  21. 21.Take 15 and take away the sum of its digits. What do you get?
  22. 22.Take 36 and take away the sum of its digits. What do you get?
  23. 23.?580 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.Take 48 and take away the sum of its digits. What do you get?
  26. 26.21?0 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  27. 27.49?7 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  28. 28.Take 34 and take away the sum of its digits. What do you get?
  29. 29.?940 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  30. 30.231? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  31. 31.73?8 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  32. 32.6?43 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  33. 33.Take 76 and take away the sum of its digits. What do you get?
  34. 34.7?6 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  35. 35.18?1 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  36. 36.Take 27 and take away the sum of its digits. What do you get?
  37. 37.7?06 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  38. 38.?05 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  39. 39.Take 78 and take away the sum of its digits. What do you get?
  40. 40.8?3 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?

Answer key

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

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