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Think of a Number Puzzles Worksheet

Maths tricks trick 6: Think of a number · Set 41 · 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.Magic trick! Think of 3. Double it, add 10, halve it, then take away 3. What number do you get?
  2. 2.Think of 12. Multiply it by 2, then add 6. What number do you end with?
  3. 3.Think of 14. Multiply it by 5, then add 1. What number do you end with?
  4. 4.I thought of a number, added 8 and then doubled it. I got 26. What was my number?
  5. 5.I thought of a number, multiplied it by 2 and added 1. I got 31. What was my number?
  6. 6.Magic trick! Think of 5. Double it, add 8, halve it, then take away 5. What number do you get?
  7. 7.Magic trick! Think of 18. Double it, add 16, halve it, then take away 18. What number do you get?
  8. 8.I thought of a number, multiplied it by 2 and added 4. I got 10. What was my number?
  9. 9.Think of 8. Multiply it by 5, then add 9. What number do you end with?
  10. 10.Magic trick! Think of 18. Double it, add 6, halve it, then take away 18. What number do you get?
  11. 11.I thought of a number, added 6 and then doubled it. I got 48. What was my number?
  12. 12.Magic trick! Think of 20. Double it, add 8, halve it, then take away 20. What number do you get?
  13. 13.Magic trick! Think of 4. Double it, add 4, halve it, then take away 4. What number do you get?
  14. 14.I thought of a number, multiplied it by 5 and added 2. I got 47. What was my number?
  15. 15.Think of 2. Multiply it by 4, then add 5. What number do you end with?
  16. 16.Magic trick! Think of 6. Double it, add 18, halve it, then take away 6. What number do you get?
  17. 17.I thought of a number, multiplied it by 4 and added 4. I got 60. What was my number?
  18. 18.Think of 6. Multiply it by 2, then add 1. What number do you end with?
  19. 19.I thought of a number, added 4 and then doubled it. I got 46. What was my number?
  20. 20.I thought of a number, multiplied it by 3 and added 3. I got 42. What was my number?
  21. 21.I thought of a number, added 3 and then doubled it. I got 42. What was my number?
  22. 22.I thought of a number, added 9 and then doubled it. I got 26. What was my number?
  23. 23.Magic trick! Think of 16. Double it, add 14, halve it, then take away 16. What number do you get?
  24. 24.Magic trick! Think of 7. Double it, add 10, halve it, then take away 7. What number do you get?
  25. 25.Magic trick! Think of 10. Double it, add 6, halve it, then take away 10. What number do you get?
  26. 26.I thought of a number, multiplied it by 3 and added 7. I got 28. What was my number?
  27. 27.Magic trick! Think of 11. Double it, add 6, halve it, then take away 11. What number do you get?
  28. 28.I thought of a number, multiplied it by 4 and added 6. I got 14. What was my number?
  29. 29.Magic trick! Think of 3. Double it, add 8, halve it, then take away 3. What number do you get?
  30. 30.I thought of a number, multiplied it by 2 and added 8. I got 22. What was my number?
  31. 31.I thought of a number, multiplied it by 2 and added 5. I got 9. What was my number?
  32. 32.I thought of a number, multiplied it by 2 and added 7. I got 19. What was my number?
  33. 33.Think of 6. Multiply it by 4, then add 5. What number do you end with?
  34. 34.Think of 6. Multiply it by 4, then add 9. What number do you end with?
  35. 35.Magic trick! Think of 8. Double it, add 10, halve it, then take away 8. What number do you get?
  36. 36.I thought of a number, added 5 and then doubled it. I got 28. What was my number?
  37. 37.Magic trick! Think of 2. Double it, add 4, halve it, then take away 2. What number do you get?
  38. 38.Think of 6. Multiply it by 5, then add 6. What number do you end with?
  39. 39.I thought of a number, multiplied it by 2 and added 2. I got 10. What was my number?
  40. 40.I thought of a number, multiplied it by 2 and added 3. I got 23. What was my number?

Answer key

  1. 5
  2. 30
  3. 71
  4. 5
  5. 15
  6. 4
  7. 8
  8. 3
  9. 49
  10. 3
  11. 18
  12. 4
  13. 2
  14. 9
  15. 13
  16. 9
  17. 14
  18. 13
  19. 19
  20. 13
  21. 18
  22. 4
  23. 7
  24. 5
  25. 3
  26. 7
  27. 3
  28. 2
  29. 4
  30. 7
  31. 2
  32. 6
  33. 29
  34. 33
  35. 5
  36. 9
  37. 2
  38. 36
  39. 4
  40. 10

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