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Think of a Number Puzzles Worksheet

Maths tricks trick 6: Think of a number · Set 214 · 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 2 and then doubled it. I got 10. What was my number?
  2. 2.Magic trick! Think of 3. Double it, add 8, halve it, then take away 3. What number do you get?
  3. 3.Think of 2. Multiply it by 4, then add 4. What number do you end with?
  4. 4.I thought of a number, added 3 and then doubled it. I got 26. What was my number?
  5. 5.I thought of a number, multiplied it by 5 and added 1. I got 11. What was my number?
  6. 6.I thought of a number, added 9 and then doubled it. I got 36. What was my number?
  7. 7.I thought of a number, added 1 and then doubled it. I got 16. What was my number?
  8. 8.I thought of a number, multiplied it by 2 and added 5. I got 15. What was my number?
  9. 9.I thought of a number, added 3 and then doubled it. I got 24. What was my number?
  10. 10.I thought of a number, multiplied it by 4 and added 6. I got 30. What was my number?
  11. 11.I thought of a number, multiplied it by 5 and added 2. I got 37. What was my number?
  12. 12.I thought of a number, multiplied it by 2 and added 7. I got 11. What was my number?
  13. 13.I thought of a number, added 6 and then doubled it. I got 30. What was my number?
  14. 14.I thought of a number, added 2 and then doubled it. I got 44. What was my number?
  15. 15.Magic trick! Think of 11. Double it, add 8, halve it, then take away 11. What number do you get?
  16. 16.I thought of a number, multiplied it by 4 and added 1. I got 29. What was my number?
  17. 17.Magic trick! Think of 15. Double it, add 4, halve it, then take away 15. What number do you get?
  18. 18.Think of 5. Multiply it by 5, then add 7. What number do you end with?
  19. 19.I thought of a number, added 2 and then doubled it. I got 30. What was my number?
  20. 20.I thought of a number, added 5 and then doubled it. I got 18. What was my number?
  21. 21.Think of 6. Multiply it by 4, then add 9. What number do you end with?
  22. 22.I thought of a number, multiplied it by 3 and added 8. I got 20. What was my number?
  23. 23.I thought of a number, added 2 and then doubled it. I got 16. What was my number?
  24. 24.Magic trick! Think of 8. Double it, add 4, halve it, then take away 8. What number do you get?
  25. 25.I thought of a number, multiplied it by 4 and added 6. I got 66. What was my number?
  26. 26.Think of 11. Multiply it by 2, then add 3. What number do you end with?
  27. 27.I thought of a number, added 3 and then doubled it. I got 14. What was my number?
  28. 28.I thought of a number, added 6 and then doubled it. I got 22. What was my number?
  29. 29.I thought of a number, multiplied it by 2 and added 2. I got 22. What was my number?
  30. 30.I thought of a number, added 8 and then doubled it. I got 28. What was my number?
  31. 31.Think of 3. Multiply it by 2, then add 4. What number do you end with?
  32. 32.Magic trick! Think of 5. Double it, add 6, halve it, then take away 5. What number do you get?
  33. 33.Magic trick! Think of 11. Double it, add 16, halve it, then take away 11. What number do you get?
  34. 34.I thought of a number, added 8 and then doubled it. I got 38. What was my number?
  35. 35.I thought of a number, multiplied it by 5 and added 8. I got 58. What was my number?
  36. 36.I thought of a number, added 9 and then doubled it. I got 28. What was my number?
  37. 37.Think of 3. Multiply it by 3, then add 1. What number do you end with?
  38. 38.I thought of a number, added 7 and then doubled it. I got 38. What was my number?
  39. 39.Think of 12. Multiply it by 2, then add 4. What number do you end with?
  40. 40.I thought of a number, multiplied it by 4 and added 4. I got 16. What was my number?

Answer key

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

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