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Digit Sum Magic Worksheet

Maths tricks trick 10: Digit-sum magic · Set 180 · 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 89 and take away the sum of its digits. What do you get?
  2. 2.54? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  3. 3.?878 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  4. 4.8?20 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  5. 5.Take 31 and take away the sum of its digits. What do you get?
  6. 6.Take 69 and take away the sum of its digits. What do you get?
  7. 7.Take 46 and take away the sum of its digits. What do you get?
  8. 8.Take 99 and take away the sum of its digits. What do you get?
  9. 9.45?6 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  10. 10.96? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  11. 11.67?2 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  12. 12.Take 33 and take away the sum of its digits. What do you get?
  13. 13.Take 25 and take away the sum of its digits. What do you get?
  14. 14.Take 34 and take away the sum of its digits. What do you get?
  15. 15.534? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  16. 16.Take 12 and take away the sum of its digits. What do you get?
  17. 17.43?2 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  18. 18.Take 19 and take away the sum of its digits. What do you get?
  19. 19.?994 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  20. 20.Take 85 and take away the sum of its digits. What do you get?
  21. 21.?667 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  22. 22.Take 58 and take away the sum of its digits. What do you get?
  23. 23.319? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  24. 24.Take 44 and take away the sum of its digits. What do you get?
  25. 25.?120 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  26. 26.Take 66 and take away the sum of its digits. What do you get?
  27. 27.574? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  28. 28.Take 49 and take away the sum of its digits. What do you get?
  29. 29.Take 45 and take away the sum of its digits. What do you get?
  30. 30.?215 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  31. 31.64?8 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  32. 32.6?81 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  33. 33.4?2 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  34. 34.Take 21 and take away the sum of its digits. What do you get?
  35. 35.Take 88 and take away the sum of its digits. What do you get?
  36. 36.Take 56 and take away the sum of its digits. What do you get?
  37. 37.Take 11 and take away the sum of its digits. What do you get?
  38. 38.?30 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  39. 39.?497 is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?
  40. 40.807? is in the 9 times table. One digit is hidden, and it is not 0. What is the hidden digit?

Answer key

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

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