“Hey Presto!”: Solution
Solution to Hey Presto!:
The conjurer simply adds up the digits in the final figure. If the result has multiple digits, he adds those, and so on until he reaches a single digit:
4 + 5 + 6 + 0 + 2 + 0 + 7 + 0 + 8 + 6 + 5 + 6 + 9 = 58
5 + 8 = 13
1 + 3 = 4
That digit is the number from step 1.
It works because all multiples of 9 eventually produce 9 when their digits are added as above; the procedure asks you to create two multiples of 9 (in steps 2 and 4) and to combine their digits and add your own. Adding the digits will thus yield 9 plus the number chosen (here, 13), and of course adding those digits will yield the number itself.
The business with the father’s first name, etc., is just smoke — any numbers at all can be used in those positions. The arithmetic will always produce the right answer.
