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Digit Sum Magic Worksheet

Maths tricks trick 10: Digit-sum magic · Set 270 · 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.?905 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  2. 2.Take 59 and take away the sum of its digits. What do you get?
  3. 3.Take 20 and take away the sum of its digits. What do you get?
  4. 4.81?5 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  5. 5.489? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  6. 6.Take 26 and take away the sum of its digits. What do you get?
  7. 7.Take 29 and take away the sum of its digits. What do you get?
  8. 8.Take 49 and take away the sum of its digits. What do you get?
  9. 9.Take 14 and take away the sum of its digits. What do you get?
  10. 10.Take 75 and take away the sum of its digits. What do you get?
  11. 11.57?8 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  12. 12.65?0 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  13. 13.?393 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  14. 14.?295 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  15. 15.7?91 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  16. 16.?715 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  17. 17.217? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  18. 18.45?6 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  19. 19.Take 57 and take away the sum of its digits. What do you get?
  20. 20.Take 11 and take away the sum of its digits. What do you get?
  21. 21.685? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  22. 22.55? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  23. 23.Take 28 and take away the sum of its digits. What do you get?
  24. 24.Take 53 and take away the sum of its digits. What do you get?
  25. 25.Take 21 and take away the sum of its digits. What do you get?
  26. 26.510? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  27. 27.?494 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  28. 28.?709 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  29. 29.38?2 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  30. 30.46? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  31. 31.3?2 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  32. 32.1?44 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  33. 33.Take 51 and take away the sum of its digits. What do you get?
  34. 34.785? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  35. 35.?448 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  36. 36.Take 54 and take away the sum of its digits. What do you get?
  37. 37.?908 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  38. 38.Take 90 and take away the sum of its digits. What do you get?
  39. 39.?20 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  40. 40.4?2 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?

Answer key

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

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