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Digit Sum Magic Worksheet

Maths tricks trick 10: Digit-sum magic · Set 76 · 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 15 and take away the sum of its digits. What do you get?
  2. 2.307? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  3. 3.Take 64 and take away the sum of its digits. What do you get?
  4. 4.76?8 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  5. 5.442? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  6. 6.Take 23 and take away the sum of its digits. What do you get?
  7. 7.Take 35 and take away the sum of its digits. What do you get?
  8. 8.5?98 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  9. 9.36?6 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  10. 10.Take 30 and take away the sum of its digits. What do you get?
  11. 11.Take 17 and take away the sum of its digits. What do you get?
  12. 12.Take 33 and take away the sum of its digits. What do you get?
  13. 13.2?48 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  14. 14.Take 29 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.?258 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  17. 17.4?79 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  18. 18.51?6 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  19. 19.Take 82 and take away the sum of its digits. What do you get?
  20. 20.Take 87 and take away the sum of its digits. What do you get?
  21. 21.6?21 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  22. 22.5?12 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  23. 23.59?3 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  24. 24.?164 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  25. 25.335? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  26. 26.226? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  27. 27.623? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  28. 28.7?51 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  29. 29.31?9 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  30. 30.Take 68 and take away the sum of its digits. What do you get?
  31. 31.20?1 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  32. 32.Take 38 and take away the sum of its digits. What do you get?
  33. 33.Take 78 and take away the sum of its digits. What do you get?
  34. 34.Take 41 and take away the sum of its digits. What do you get?
  35. 35.614? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  36. 36.Take 49 and take away the sum of its digits. What do you get?
  37. 37.?511 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  38. 38.?974 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  39. 39.Take 59 and take away the sum of its digits. What do you get?
  40. 40.12?0 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. 8
  3. 54
  4. 6
  5. 8
  6. 18
  7. 27
  8. 5
  9. 3
  10. 27
  11. 9
  12. 27
  13. 4
  14. 18
  15. 36
  16. 3
  17. 7
  18. 6
  19. 72
  20. 72
  21. 9
  22. 1
  23. 1
  24. 7
  25. 7
  26. 8
  27. 7
  28. 5
  29. 5
  30. 54
  31. 6
  32. 27
  33. 63
  34. 36
  35. 7
  36. 36
  37. 2
  38. 7
  39. 45
  40. 6

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