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Think of a Number Puzzles Worksheet

Maths tricks trick 6: Think of a number · Set 84 · 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.Think of 6. Multiply it by 5, then add 3. What number do you end with?
  2. 2.Think of 6. Multiply it by 3, then add 8. What number do you end with?
  3. 3.I thought of a number, multiplied it by 3 and added 9. I got 30. What was my number?
  4. 4.Think of 11. Multiply it by 5, then add 2. What number do you end with?
  5. 5.Think of 7. Multiply it by 2, then add 1. What number do you end with?
  6. 6.Think of 14. Multiply it by 3, then add 2. What number do you end with?
  7. 7.I thought of a number, added 4 and then doubled it. I got 18. What was my number?
  8. 8.Think of 14. Multiply it by 3, then add 1. What number do you end with?
  9. 9.I thought of a number, added 7 and then doubled it. I got 28. What was my number?
  10. 10.Magic trick! Think of 11. Double it, add 18, halve it, then take away 11. What number do you get?
  11. 11.I thought of a number, multiplied it by 5 and added 3. I got 78. What was my number?
  12. 12.Think of 9. Multiply it by 2, then add 5. What number do you end with?
  13. 13.I thought of a number, multiplied it by 5 and added 5. I got 30. What was my number?
  14. 14.I thought of a number, added 8 and then doubled it. I got 50. What was my number?
  15. 15.Magic trick! Think of 17. Double it, add 16, halve it, then take away 17. What number do you get?
  16. 16.Magic trick! Think of 3. Double it, add 4, halve it, then take away 3. What number do you get?
  17. 17.Magic trick! Think of 4. Double it, add 18, halve it, then take away 4. What number do you get?
  18. 18.Think of 13. Multiply it by 4, then add 5. What number do you end with?
  19. 19.Magic trick! Think of 13. Double it, add 16, halve it, then take away 13. What number do you get?
  20. 20.Think of 2. Multiply it by 2, then add 1. What number do you end with?
  21. 21.Think of 14. Multiply it by 2, then add 8. What number do you end with?
  22. 22.I thought of a number, added 1 and then doubled it. I got 18. What was my number?
  23. 23.Magic trick! Think of 10. Double it, add 16, halve it, then take away 10. What number do you get?
  24. 24.Magic trick! Think of 11. Double it, add 12, halve it, then take away 11. What number do you get?
  25. 25.I thought of a number, added 4 and then doubled it. I got 22. What was my number?
  26. 26.I thought of a number, multiplied it by 2 and added 2. I got 30. What was my number?
  27. 27.I thought of a number, added 1 and then doubled it. I got 26. What was my number?
  28. 28.Think of 4. Multiply it by 4, then add 5. What number do you end with?
  29. 29.I thought of a number, multiplied it by 3 and added 4. I got 34. What was my number?
  30. 30.Think of 13. Multiply it by 3, then add 1. What number do you end with?
  31. 31.I thought of a number, multiplied it by 4 and added 2. I got 42. What was my number?
  32. 32.Magic trick! Think of 4. Double it, add 6, halve it, then take away 4. What number do you get?
  33. 33.I thought of a number, added 4 and then doubled it. I got 42. What was my number?
  34. 34.I thought of a number, multiplied it by 2 and added 8. I got 18. What was my number?
  35. 35.Magic trick! Think of 11. Double it, add 8, halve it, then take away 11. What number do you get?
  36. 36.I thought of a number, multiplied it by 2 and added 3. I got 31. What was my number?
  37. 37.I thought of a number, added 4 and then doubled it. I got 36. What was my number?
  38. 38.Think of 12. Multiply it by 3, then add 3. What number do you end with?
  39. 39.I thought of a number, multiplied it by 5 and added 5. I got 45. What was my number?
  40. 40.I thought of a number, multiplied it by 5 and added 4. I got 29. What was my number?

Answer key

  1. 33
  2. 26
  3. 7
  4. 57
  5. 15
  6. 44
  7. 5
  8. 43
  9. 7
  10. 9
  11. 15
  12. 23
  13. 5
  14. 17
  15. 8
  16. 2
  17. 9
  18. 57
  19. 8
  20. 5
  21. 36
  22. 8
  23. 8
  24. 6
  25. 7
  26. 14
  27. 12
  28. 21
  29. 10
  30. 40
  31. 10
  32. 3
  33. 17
  34. 5
  35. 4
  36. 14
  37. 14
  38. 39
  39. 8
  40. 5

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