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Digit Sum Magic Worksheet

Maths tricks trick 10: Digit-sum magic · Set 115 · 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 30 and take away the sum of its digits. What do you get?
  2. 2.Take 39 and take away the sum of its digits. What do you get?
  3. 3.642? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  4. 4.?352 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  5. 5.Take 83 and take away the sum of its digits. What do you get?
  6. 6.?902 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  7. 7.2?70 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  8. 8.Take 52 and take away the sum of its digits. What do you get?
  9. 9.53?7 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  10. 10.?069 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  11. 11.Take 61 and take away the sum of its digits. What do you get?
  12. 12.5?8 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  13. 13.Take 48 and take away the sum of its digits. What do you get?
  14. 14.703? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  15. 15.?255 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  16. 16.51?0 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  17. 17.51?7 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  18. 18.?658 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  19. 19.?79 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  20. 20.6?6 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  21. 21.212? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  22. 22.Take 92 and take away the sum of its digits. What do you get?
  23. 23.2?38 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  24. 24.?84 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  25. 25.?536 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  26. 26.?012 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  27. 27.Take 86 and take away the sum of its digits. What do you get?
  28. 28.Take 18 and take away the sum of its digits. What do you get?
  29. 29.Take 50 and take away the sum of its digits. What do you get?
  30. 30.Take 85 and take away the sum of its digits. What do you get?
  31. 31.Take 28 and take away the sum of its digits. What do you get?
  32. 32.?625 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  33. 33.Take 12 and take away the sum of its digits. What do you get?
  34. 34.Take 93 and take away the sum of its digits. What do you get?
  35. 35.Take 78 and take away the sum of its digits. What do you get?
  36. 36.10?3 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  37. 37.Take 55 and take away the sum of its digits. What do you get?
  38. 38.8?43 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  39. 39.Take 26 and take away the sum of its digits. What do you get?
  40. 40.486? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?

Answer key

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

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