Think of a Number Puzzles Worksheet

Maths tricks trick 6: Think of a number · Set 29 · 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.Magic trick! Think of 3. Double it, add 4, halve it, then take away 3. What number do you get?
2. 2.Think of 7. Multiply it by 5, then add 1. What number do you end with?
3. 3.I thought of a number, multiplied it by 5 and added 7. I got 82. What was my number?
4. 4.I thought of a number, added 1 and then doubled it. I got 10. What was my number?
5. 5.I thought of a number, added 3 and then doubled it. I got 38. What was my number?
6. 6.Magic trick! Think of 19. Double it, add 18, halve it, then take away 19. What number do you get?
7. 7.Think of 13. Multiply it by 4, then add 6. What number do you end with?
8. 8.Magic trick! Think of 7. Double it, add 8, halve it, then take away 7. What number do you get?
9. 9.Think of 12. Multiply it by 2, then add 3. What number do you end with?
10. 10.I thought of a number, multiplied it by 2 and added 5. I got 29. What was my number?
11. 11.Think of 5. Multiply it by 3, then add 4. What number do you end with?
12. 12.I thought of a number, added 5 and then doubled it. I got 36. What was my number?
13. 13.I thought of a number, added 3 and then doubled it. I got 34. What was my number?
14. 14.Magic trick! Think of 8. Double it, add 4, halve it, then take away 8. What number do you get?
15. 15.Think of 9. Multiply it by 2, then add 1. What number do you end with?
16. 16.Magic trick! Think of 6. Double it, add 10, halve it, then take away 6. What number do you get?
17. 17.I thought of a number, added 2 and then doubled it. I got 12. What was my number?
18. 18.Think of 3. Multiply it by 2, then add 8. What number do you end with?
19. 19.I thought of a number, multiplied it by 4 and added 9. I got 25. What was my number?
20. 20.Think of 4. Multiply it by 2, then add 2. What number do you end with?
21. 21.Think of 6. Multiply it by 2, then add 7. What number do you end with?
22. 22.Think of 2. Multiply it by 4, then add 3. What number do you end with?
23. 23.I thought of a number, multiplied it by 2 and added 3. I got 15. What was my number?
24. 24.Think of 11. Multiply it by 2, then add 8. What number do you end with?
25. 25.I thought of a number, multiplied it by 2 and added 4. I got 34. What was my number?
26. 26.Magic trick! Think of 9. Double it, add 10, halve it, then take away 9. What number do you get?
27. 27.Magic trick! Think of 10. Double it, add 12, halve it, then take away 10. What number do you get?
28. 28.Think of 5. Multiply it by 5, then add 4. What number do you end with?
29. 29.Think of 4. Multiply it by 3, then add 8. What number do you end with?
30. 30.Magic trick! Think of 20. Double it, add 4, halve it, then take away 20. What number do you get?
31. 31.I thought of a number, added 7 and then doubled it. I got 48. What was my number?
32. 32.Think of 10. Multiply it by 5, then add 8. What number do you end with?
33. 33.Magic trick! Think of 2. Double it, add 10, halve it, then take away 2. What number do you get?
34. 34.I thought of a number, added 8 and then doubled it. I got 32. What was my number?
35. 35.Think of 5. Multiply it by 2, then add 3. What number do you end with?
36. 36.I thought of a number, added 9 and then doubled it. I got 24. What was my number?
37. 37.Think of 7. Multiply it by 2, then add 3. What number do you end with?
38. 38.Magic trick! Think of 3. Double it, add 6, halve it, then take away 3. What number do you get?
39. 39.Magic trick! Think of 15. Double it, add 8, halve it, then take away 15. What number do you get?
40. 40.Magic trick! Think of 3. Double it, add 8, halve it, then take away 3. What number do you get?

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