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Digit Sum Magic Worksheet

Maths tricks trick 10: Digit-sum magic · Set 55 · 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 11 and take away the sum of its digits. What do you get?
  2. 2.Take 21 and take away the sum of its digits. What do you get?
  3. 3.513? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  4. 4.79? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  5. 5.Take 35 and take away the sum of its digits. What do you get?
  6. 6.527? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  7. 7.41?5 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  8. 8.Take 33 and take away the sum of its digits. What do you get?
  9. 9.Take 96 and take away the sum of its digits. What do you get?
  10. 10.?583 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  11. 11.24?9 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  12. 12.Take 51 and take away the sum of its digits. What do you get?
  13. 13.Take 67 and take away the sum of its digits. What do you get?
  14. 14.Take 19 and take away the sum of its digits. What do you get?
  15. 15.Take 43 and take away the sum of its digits. What do you get?
  16. 16.Take 22 and take away the sum of its digits. What do you get?
  17. 17.?01 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  18. 18.5?7 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  19. 19.2?3 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  20. 20.?362 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  21. 21.2?50 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  22. 22.419? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  23. 23.Take 90 and take away the sum of its digits. What do you get?
  24. 24.Take 99 and take away the sum of its digits. What do you get?
  25. 25.?81 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  26. 26.353? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  27. 27.?745 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  28. 28.Take 71 and take away the sum of its digits. What do you get?
  29. 29.Take 81 and take away the sum of its digits. What do you get?
  30. 30.58?9 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  31. 31.39?9 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  32. 32.179? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  33. 33.?463 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  34. 34.600? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  35. 35.187? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  36. 36.?374 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  37. 37.?735 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  38. 38.?33 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  39. 39.?074 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  40. 40.8?86 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. 18
  3. 9
  4. 2
  5. 27
  6. 4
  7. 8
  8. 27
  9. 81
  10. 2
  11. 3
  12. 45
  13. 54
  14. 9
  15. 36
  16. 18
  17. 8
  18. 6
  19. 4
  20. 7
  21. 2
  22. 4
  23. 81
  24. 81
  25. 9
  26. 7
  27. 2
  28. 63
  29. 72
  30. 5
  31. 6
  32. 1
  33. 5
  34. 3
  35. 2
  36. 4
  37. 3
  38. 3
  39. 7
  40. 5

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