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Think of a Number Puzzles Worksheet

Maths tricks trick 6: Think of a number · Set 175 · 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, added 6 and then doubled it. I got 38. What was my number?
  2. 2.I thought of a number, multiplied it by 4 and added 9. I got 37. What was my number?
  3. 3.I thought of a number, multiplied it by 3 and added 6. I got 39. What was my number?
  4. 4.Think of 4. Multiply it by 3, then add 1. What number do you end with?
  5. 5.I thought of a number, added 6 and then doubled it. I got 26. What was my number?
  6. 6.Think of 11. Multiply it by 2, then add 6. What number do you end with?
  7. 7.I thought of a number, added 8 and then doubled it. I got 32. What was my number?
  8. 8.Magic trick! Think of 13. Double it, add 18, halve it, then take away 13. What number do you get?
  9. 9.I thought of a number, multiplied it by 3 and added 9. I got 54. What was my number?
  10. 10.Magic trick! Think of 7. Double it, add 12, halve it, then take away 7. What number do you get?
  11. 11.I thought of a number, added 9 and then doubled it. I got 30. What was my number?
  12. 12.I thought of a number, added 9 and then doubled it. I got 40. What was my number?
  13. 13.I thought of a number, added 2 and then doubled it. I got 12. What was my number?
  14. 14.I thought of a number, multiplied it by 5 and added 2. I got 42. What was my number?
  15. 15.I thought of a number, multiplied it by 2 and added 2. I got 10. What was my number?
  16. 16.Magic trick! Think of 11. Double it, add 18, halve it, then take away 11. What number do you get?
  17. 17.I thought of a number, added 7 and then doubled it. I got 50. What was my number?
  18. 18.I thought of a number, added 9 and then doubled it. I got 28. What was my number?
  19. 19.I thought of a number, multiplied it by 4 and added 9. I got 29. What was my number?
  20. 20.Think of 4. Multiply it by 5, then add 8. What number do you end with?
  21. 21.Magic trick! Think of 2. Double it, add 8, halve it, then take away 2. What number do you get?
  22. 22.I thought of a number, added 1 and then doubled it. I got 28. What was my number?
  23. 23.Magic trick! Think of 8. Double it, add 14, halve it, then take away 8. What number do you get?
  24. 24.I thought of a number, multiplied it by 5 and added 7. I got 82. What was my number?
  25. 25.I thought of a number, multiplied it by 5 and added 4. I got 59. What was my number?
  26. 26.Magic trick! Think of 6. Double it, add 18, halve it, then take away 6. What number do you get?
  27. 27.Think of 6. Multiply it by 2, then add 1. What number do you end with?
  28. 28.Magic trick! Think of 3. Double it, add 12, halve it, then take away 3. What number do you get?
  29. 29.Magic trick! Think of 9. Double it, add 6, halve it, then take away 9. What number do you get?
  30. 30.Magic trick! Think of 12. Double it, add 4, halve it, then take away 12. What number do you get?
  31. 31.I thought of a number, multiplied it by 5 and added 9. I got 59. What was my number?
  32. 32.I thought of a number, multiplied it by 2 and added 1. I got 9. What was my number?
  33. 33.Magic trick! Think of 4. Double it, add 16, halve it, then take away 4. What number do you get?
  34. 34.I thought of a number, added 3 and then doubled it. I got 30. What was my number?
  35. 35.I thought of a number, added 5 and then doubled it. I got 26. What was my number?
  36. 36.I thought of a number, multiplied it by 4 and added 1. I got 29. What was my number?
  37. 37.Think of 7. Multiply it by 2, then add 4. What number do you end with?
  38. 38.Think of 15. Multiply it by 2, then add 7. What number do you end with?
  39. 39.I thought of a number, added 3 and then doubled it. I got 32. What was my number?
  40. 40.I thought of a number, multiplied it by 2 and added 3. I got 15. What was my number?

Answer key

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

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