Think of a Number Puzzles Worksheet

Maths tricks trick 6: Think of a number · Set 165 · 40 questions

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.

1. 1.Think of 4. Multiply it by 5, then add 3. What number do you end with?
2. 2.I thought of a number, multiplied it by 2 and added 3. I got 25. What was my number?
3. 3.Magic trick! Think of 4. Double it, add 16, halve it, then take away 4. What number do you get?
4. 4.Magic trick! Think of 3. Double it, add 14, halve it, then take away 3. What number do you get?
5. 5.Think of 4. Multiply it by 2, then add 6. What number do you end with?
6. 6.Think of 7. Multiply it by 4, then add 1. What number do you end with?
7. 7.I thought of a number, multiplied it by 2 and added 1. I got 27. What was my number?
8. 8.Think of 12. Multiply it by 4, then add 3. What number do you end with?
9. 9.I thought of a number, multiplied it by 2 and added 3. I got 33. What was my number?
10. 10.Magic trick! Think of 17. Double it, add 18, halve it, then take away 17. What number do you get?
11. 11.I thought of a number, added 2 and then doubled it. I got 42. What was my number?
12. 12.Think of 10. Multiply it by 2, then add 1. What number do you end with?
13. 13.Think of 10. Multiply it by 5, then add 3. What number do you end with?
14. 14.Magic trick! Think of 18. Double it, add 14, halve it, then take away 18. What number do you get?
15. 15.I thought of a number, multiplied it by 3 and added 3. I got 21. What was my number?
16. 16.I thought of a number, multiplied it by 5 and added 7. I got 62. What was my number?
17. 17.Think of 12. Multiply it by 2, then add 1. What number do you end with?
18. 18.I thought of a number, multiplied it by 3 and added 9. I got 27. What was my number?
19. 19.I thought of a number, multiplied it by 2 and added 8. I got 38. What was my number?
20. 20.I thought of a number, added 5 and then doubled it. I got 40. What was my number?
21. 21.Think of 5. Multiply it by 3, then add 3. What number do you end with?
22. 22.I thought of a number, multiplied it by 4 and added 2. I got 38. What was my number?
23. 23.I thought of a number, multiplied it by 5 and added 5. I got 25. What was my number?
24. 24.Magic trick! Think of 5. Double it, add 4, halve it, then take away 5. What number do you get?
25. 25.Magic trick! Think of 3. Double it, add 6, halve it, then take away 3. What number do you get?
26. 26.I thought of a number, multiplied it by 3 and added 5. I got 44. What was my number?
27. 27.I thought of a number, multiplied it by 4 and added 7. I got 31. What was my number?
28. 28.Magic trick! Think of 2. Double it, add 16, halve it, then take away 2. What number do you get?
29. 29.Think of 12. Multiply it by 5, then add 3. What number do you end with?
30. 30.Think of 7. Multiply it by 4, then add 8. What number do you end with?
31. 31.Think of 3. Multiply it by 3, then add 4. What number do you end with?
32. 32.I thought of a number, added 7 and then doubled it. I got 30. What was my number?
33. 33.I thought of a number, added 2 and then doubled it. I got 10. What was my number?
34. 34.I thought of a number, multiplied it by 5 and added 9. I got 19. What was my number?
35. 35.Magic trick! Think of 17. Double it, add 12, halve it, then take away 17. What number do you get?
36. 36.I thought of a number, added 7 and then doubled it. I got 42. What was my number?
37. 37.Think of 15. Multiply it by 4, then add 3. What number do you end with?
38. 38.I thought of a number, multiplied it by 3 and added 6. I got 15. What was my number?
39. 39.I thought of a number, added 9 and then doubled it. I got 52. What was my number?
40. 40.I thought of a number, multiplied it by 5 and added 6. I got 81. What was my number?

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