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Puzzle #204: Can you work out what number my son thought of?

Can you solve this week’s arithmetical puzzle, Think of a number? Plus the answer to puzzle #203

11 January 2023

#204 Think of a number

Set by Peter Rowlett

My son’s book of mathematical magic tricks includes this one:

1. Think of a whole number from 1 to 50.

2. Add 9 and double the result.

3. Multiply by 6 and add 12.

4. Subtract 60.

5. Divide by 12 and subtract 4.

6. Subtract your original number.

7. And the answer is (drumroll…) 1!

Unfortunately, when he is reading, my son sometimes repeats a line and sometimes he skips one. That happened with this trick. He did one of the lines twice and then missed the final instruction to …

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