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Digit Sum Magic Worksheet

Maths tricks trick 10: Digit-sum magic · Set 30 · 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 19 and take away the sum of its digits. What do you get?
  2. 2.17?7 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  3. 3.?010 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  4. 4.405? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  5. 5.?986 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  6. 6.Take 31 and take away the sum of its digits. What do you get?
  7. 7.Take 49 and take away the sum of its digits. What do you get?
  8. 8.?386 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  9. 9.Take 44 and take away the sum of its digits. What do you get?
  10. 10.Take 46 and take away the sum of its digits. What do you get?
  11. 11.749? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  12. 12.99? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  13. 13.Take 77 and take away the sum of its digits. What do you get?
  14. 14.Take 98 and take away the sum of its digits. What do you get?
  15. 15.Take 40 and take away the sum of its digits. What do you get?
  16. 16.64?5 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  17. 17.4?1 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  18. 18.Take 24 and take away the sum of its digits. What do you get?
  19. 19.Take 97 and take away the sum of its digits. What do you get?
  20. 20.3?86 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  21. 21.7?59 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  22. 22.2?36 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  23. 23.?080 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  24. 24.Take 11 and take away the sum of its digits. What do you get?
  25. 25.19?4 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  26. 26.Take 89 and take away the sum of its digits. What do you get?
  27. 27.764? 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.?101 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  30. 30.?645 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  31. 31.50?3 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  32. 32.3?68 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  33. 33.79?2 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  34. 34.8?27 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  35. 35.622? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  36. 36.54?9 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  37. 37.521? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  38. 38.29?9 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  39. 39.649? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  40. 40.8?75 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?

Answer key

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

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