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Digit Sum Magic Worksheet

Maths tricks trick 10: Digit-sum magic · Set 691 · 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. 2.783? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  3. 3.Take 15 and take away the sum of its digits. What do you get?
  4. 4.3?27 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  5. 5.42?1 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  6. 6.Take 66 and take away the sum of its digits. What do you get?
  7. 7.540? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  8. 8.Take 56 and take away the sum of its digits. What do you get?
  9. 9.1?74 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  10. 10.8?65 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  11. 11.?271 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  12. 12.?933 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  13. 13.Take 98 and take away the sum of its digits. What do you get?
  14. 14.461? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  15. 15.Take 95 and take away the sum of its digits. What do you get?
  16. 16.Take 42 and take away the sum of its digits. What do you get?
  17. 17.?841 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  18. 18.800? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  19. 19.58?1 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  20. 20.Take 75 and take away the sum of its digits. What do you get?
  21. 21.77?7 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  22. 22.?079 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  23. 23.Take 94 and take away the sum of its digits. What do you get?
  24. 24.108? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  25. 25.5?16 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  26. 26.Take 90 and take away the sum of its digits. What do you get?
  27. 27.?047 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  28. 28.Take 38 and take away the sum of its digits. What do you get?
  29. 29.Take 77 and take away the sum of its digits. What do you get?
  30. 30.1?29 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  31. 31.Take 97 and take away the sum of its digits. What do you get?
  32. 32.?593 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  33. 33.?793 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  34. 34.Take 11 and take away the sum of its digits. What do you get?
  35. 35.32? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  36. 36.?879 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  37. 37.Take 70 and take away the sum of its digits. What do you get?
  38. 38.3?44 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  39. 39.Take 43 and take away the sum of its digits. What do you get?
  40. 40.477? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?

Answer key

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

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