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Think of a Number Puzzles Worksheet

Maths tricks trick 6: Think of a number · Set 26 · 40 questions
TalentJR

The trick (Undo the steps): Going forwards: do the steps in order. Going backwards: start from the result and undo each step, last one first. Undo + with −, × with ÷, and doubling with halving.

NameDateTime takenScore ___ / 40
  1. 1.I thought of a number, multiplied it by 2 and added 3. I got 21. What was my number?
  2. 2.Magic trick! Think of 5. Double it, add 16, halve it, then take away 5. What number do you get?
  3. 3.Magic trick! Think of 9. Double it, add 6, halve it, then take away 9. What number do you get?
  4. 4.I thought of a number, added 3 and then doubled it. I got 16. What was my number?
  5. 5.Magic trick! Think of 15. Double it, add 16, halve it, then take away 15. What number do you get?
  6. 6.Think of 5. Multiply it by 4, then add 4. What number do you end with?
  7. 7.Magic trick! Think of 3. Double it, add 6, halve it, then take away 3. What number do you get?
  8. 8.I thought of a number, added 6 and then doubled it. I got 44. What was my number?
  9. 9.I thought of a number, multiplied it by 4 and added 5. I got 53. What was my number?
  10. 10.I thought of a number, added 2 and then doubled it. I got 30. What was my number?
  11. 11.Think of 14. Multiply it by 2, then add 7. What number do you end with?
  12. 12.I thought of a number, multiplied it by 4 and added 1. I got 13. What was my number?
  13. 13.Think of 9. Multiply it by 3, then add 6. What number do you end with?
  14. 14.I thought of a number, multiplied it by 3 and added 6. I got 12. What was my number?
  15. 15.I thought of a number, multiplied it by 2 and added 7. I got 27. What was my number?
  16. 16.I thought of a number, multiplied it by 2 and added 7. I got 23. What was my number?
  17. 17.I thought of a number, multiplied it by 2 and added 9. I got 37. What was my number?
  18. 18.Magic trick! Think of 11. Double it, add 12, halve it, then take away 11. What number do you get?
  19. 19.I thought of a number, multiplied it by 4 and added 3. I got 15. What was my number?
  20. 20.I thought of a number, multiplied it by 2 and added 2. I got 10. What was my number?
  21. 21.Magic trick! Think of 6. Double it, add 6, halve it, then take away 6. What number do you get?
  22. 22.I thought of a number, added 5 and then doubled it. I got 16. What was my number?
  23. 23.Magic trick! Think of 11. Double it, add 6, halve it, then take away 11. What number do you get?
  24. 24.I thought of a number, multiplied it by 4 and added 1. I got 61. What was my number?
  25. 25.I thought of a number, multiplied it by 4 and added 6. I got 26. What was my number?
  26. 26.Think of 14. Multiply it by 4, then add 3. What number do you end with?
  27. 27.Magic trick! Think of 2. Double it, add 4, halve it, then take away 2. What number do you get?
  28. 28.I thought of a number, multiplied it by 5 and added 1. I got 66. What was my number?
  29. 29.Magic trick! Think of 6. Double it, add 4, halve it, then take away 6. What number do you get?
  30. 30.I thought of a number, multiplied it by 5 and added 6. I got 31. What was my number?
  31. 31.I thought of a number, multiplied it by 3 and added 2. I got 38. What was my number?
  32. 32.Magic trick! Think of 6. Double it, add 12, halve it, then take away 6. What number do you get?
  33. 33.I thought of a number, added 3 and then doubled it. I got 12. What was my number?
  34. 34.I thought of a number, multiplied it by 3 and added 4. I got 13. What was my number?
  35. 35.I thought of a number, multiplied it by 4 and added 9. I got 65. What was my number?
  36. 36.Think of 3. Multiply it by 3, then add 5. What number do you end with?
  37. 37.I thought of a number, multiplied it by 2 and added 6. I got 16. What was my number?
  38. 38.Magic trick! Think of 2. Double it, add 6, halve it, then take away 2. What number do you get?
  39. 39.Magic trick! Think of 19. Double it, add 6, halve it, then take away 19. What number do you get?
  40. 40.I thought of a number, multiplied it by 4 and added 2. I got 58. What was my number?

Answer key

  1. 9
  2. 8
  3. 3
  4. 5
  5. 8
  6. 24
  7. 3
  8. 16
  9. 12
  10. 13
  11. 35
  12. 3
  13. 33
  14. 2
  15. 10
  16. 8
  17. 14
  18. 6
  19. 3
  20. 4
  21. 3
  22. 3
  23. 3
  24. 15
  25. 5
  26. 59
  27. 2
  28. 13
  29. 2
  30. 5
  31. 12
  32. 6
  33. 3
  34. 3
  35. 14
  36. 14
  37. 5
  38. 3
  39. 3
  40. 14

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