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Digit Sum Magic Worksheet

Maths tricks trick 10: Digit-sum magic · Set 825 · 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 99 and take away the sum of its digits. What do you get?
  2. 2.50?4 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  3. 3.33?0 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  4. 4.Take 25 and take away the sum of its digits. What do you get?
  5. 5.50?9 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  6. 6.?658 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  7. 7.85?9 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  8. 8.Take 20 and take away the sum of its digits. What do you get?
  9. 9.Take 81 and take away the sum of its digits. What do you get?
  10. 10.?080 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  11. 11.Take 29 and take away the sum of its digits. What do you get?
  12. 12.?050 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  13. 13.165? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  14. 14.Take 58 and take away the sum of its digits. What do you get?
  15. 15.90? 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 59 and take away the sum of its digits. What do you get?
  18. 18.45?2 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  19. 19.628? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  20. 20.?93 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  21. 21.264? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  22. 22.?138 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  23. 23.?37 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  24. 24.Take 46 and take away the sum of its digits. What do you get?
  25. 25.7?15 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  26. 26.Take 93 and take away the sum of its digits. What do you get?
  27. 27.Take 31 and take away the sum of its digits. What do you get?
  28. 28.4?1 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  29. 29.8?83 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  30. 30.27?9 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  31. 31.323? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  32. 32.31?5 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  33. 33.?925 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  34. 34.70? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  35. 35.3?77 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  36. 36.Take 28 and take away the sum of its digits. What do you get?
  37. 37.?730 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  38. 38.794? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  39. 39.362? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  40. 40.?991 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?

Answer key

  1. 81
  2. 9
  3. 3
  4. 18
  5. 4
  6. 8
  7. 5
  8. 18
  9. 72
  10. 1
  11. 18
  12. 4
  13. 6
  14. 45
  15. 9
  16. 54
  17. 45
  18. 7
  19. 2
  20. 6
  21. 6
  22. 6
  23. 8
  24. 36
  25. 5
  26. 81
  27. 27
  28. 4
  29. 8
  30. 9
  31. 1
  32. 9
  33. 2
  34. 2
  35. 1
  36. 18
  37. 8
  38. 7
  39. 7
  40. 8

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