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Digit Sum Magic Worksheet

Maths tricks trick 10: Digit-sum magic · Set 360 · 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 18 and take away the sum of its digits. What do you get?
  2. 2.4?42 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  3. 3.85?1 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  4. 4.Take 14 and take away the sum of its digits. What do you get?
  5. 5.7?63 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  6. 6.220? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  7. 7.775? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  8. 8.Take 23 and take away the sum of its digits. What do you get?
  9. 9.?025 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  10. 10.11?2 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  11. 11.18?4 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  12. 12.6?17 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  13. 13.3?37 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  14. 14.Take 13 and take away the sum of its digits. What do you get?
  15. 15.448? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  16. 16.Take 66 and take away the sum of its digits. What do you get?
  17. 17.Take 70 and take away the sum of its digits. What do you get?
  18. 18.?99 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  19. 19.Take 74 and take away the sum of its digits. What do you get?
  20. 20.Take 99 and take away the sum of its digits. What do you get?
  21. 21.31?6 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  22. 22.1?34 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  23. 23.Take 32 and take away the sum of its digits. What do you get?
  24. 24.Take 25 and take away the sum of its digits. What do you get?
  25. 25.5?4 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  26. 26.104? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  27. 27.?452 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  28. 28.Take 63 and take away the sum of its digits. What do you get?
  29. 29.Take 21 and take away the sum of its digits. What do you get?
  30. 30.Take 85 and take away the sum of its digits. What do you get?
  31. 31.?580 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  32. 32.Take 35 and take away the sum of its digits. What do you get?
  33. 33.?206 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  34. 34.896? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  35. 35.Take 17 and take away the sum of its digits. What do you get?
  36. 36.Take 60 and take away the sum of its digits. What do you get?
  37. 37.10? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  38. 38.22?5 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  39. 39.56?5 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  40. 40.249? 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. 4
  4. 9
  5. 2
  6. 5
  7. 8
  8. 18
  9. 2
  10. 5
  11. 5
  12. 4
  13. 5
  14. 9
  15. 2
  16. 54
  17. 63
  18. 9
  19. 63
  20. 81
  21. 8
  22. 1
  23. 27
  24. 18
  25. 9
  26. 4
  27. 7
  28. 54
  29. 18
  30. 72
  31. 5
  32. 27
  33. 1
  34. 4
  35. 9
  36. 54
  37. 8
  38. 9
  39. 2
  40. 3

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