Think of a Number Puzzles Worksheet

Maths tricks trick 6: Think of a number · Set 115 · 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.I thought of a number, multiplied it by 2 and added 1. I got 5. What was my number?
2. 2.Think of 13. Multiply it by 5, then add 3. What number do you end with?
3. 3.Magic trick! Think of 11. Double it, add 10, halve it, then take away 11. What number do you get?
4. 4.Think of 11. Multiply it by 4, then add 5. What number do you end with?
5. 5.Magic trick! Think of 19. Double it, add 6, halve it, then take away 19. What number do you get?
6. 6.I thought of a number, multiplied it by 5 and added 7. I got 72. What was my number?
7. 7.I thought of a number, multiplied it by 2 and added 2. I got 16. What was my number?
8. 8.I thought of a number, added 1 and then doubled it. I got 30. What was my number?
9. 9.Magic trick! Think of 14. Double it, add 8, halve it, then take away 14. What number do you get?
10. 10.Think of 5. Multiply it by 2, then add 8. What number do you end with?
11. 11.Magic trick! Think of 16. Double it, add 4, halve it, then take away 16. What number do you get?
12. 12.Magic trick! Think of 3. Double it, add 16, halve it, then take away 3. What number do you get?
13. 13.Think of 5. Multiply it by 3, then add 7. What number do you end with?
14. 14.Think of 10. Multiply it by 5, then add 4. What number do you end with?
15. 15.Magic trick! Think of 2. Double it, add 4, halve it, then take away 2. What number do you get?
16. 16.Think of 15. Multiply it by 4, then add 1. What number do you end with?
17. 17.Magic trick! Think of 10. Double it, add 18, halve it, then take away 10. What number do you get?
18. 18.Magic trick! Think of 17. Double it, add 16, halve it, then take away 17. What number do you get?
19. 19.Think of 12. Multiply it by 4, then add 3. What number do you end with?
20. 20.Think of 10. Multiply it by 4, then add 7. What number do you end with?
21. 21.I thought of a number, multiplied it by 4 and added 6. I got 66. What was my number?
22. 22.Magic trick! Think of 7. Double it, add 16, halve it, then take away 7. What number do you get?
23. 23.I thought of a number, added 4 and then doubled it. I got 48. What was my number?
24. 24.I thought of a number, added 7 and then doubled it. I got 26. What was my number?
25. 25.Think of 8. Multiply it by 2, then add 7. What number do you end with?
26. 26.I thought of a number, multiplied it by 5 and added 7. I got 57. What was my number?
27. 27.Magic trick! Think of 12. Double it, add 10, halve it, then take away 12. What number do you get?
28. 28.I thought of a number, multiplied it by 2 and added 9. I got 37. What was my number?
29. 29.I thought of a number, multiplied it by 5 and added 3. I got 18. What was my number?
30. 30.I thought of a number, added 8 and then doubled it. I got 24. What was my number?
31. 31.Magic trick! Think of 4. Double it, add 16, halve it, then take away 4. What number do you get?
32. 32.I thought of a number, added 9 and then doubled it. I got 40. What was my number?
33. 33.Think of 10. Multiply it by 4, then add 1. What number do you end with?
34. 34.Think of 5. Multiply it by 2, then add 4. What number do you end with?
35. 35.I thought of a number, multiplied it by 2 and added 3. I got 23. What was my number?
36. 36.Think of 8. Multiply it by 5, then add 1. What number do you end with?
37. 37.Magic trick! Think of 18. Double it, add 16, halve it, then take away 18. What number do you get?
38. 38.Think of 3. Multiply it by 4, then add 9. What number do you end with?
39. 39.I thought of a number, multiplied it by 2 and added 7. I got 15. What was my number?
40. 40.I thought of a number, multiplied it by 2 and added 7. I got 37. What was my number?

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