The key lies in a characteristic of the
number 9. If you transpose the digits in a number and subtract the
smaller number from the larger, the difference is always evenly divisible
by 9.
__Example 1__
4321 rearranged to 1423
4321 minus 1423 = 2898
I choose to circle the **9**, leaving
the numbers 2, 8 & 8 to be typed in.
The only number that may be added to
the sequence 2+8+8 and be divisible evenly by 9 is **9** (the digit
I circled). [2+8+8+9=27]
__Example 2__
6734 rearranged to 7346
7346 minus 6734 = 612
I choose to circle the **6**, leaving
the numbers 1 & 2 to be typed in.
The only number that may be added to the
sequence 1+2 and be divisible evenly by 9 is **6**
(the digit I circled). [1+2+6=9]
__Example 3__
578 rearranged to 857
857 minus 578 = 279
I choose to circle the **2**, leaving
the numbers 7 & 9 to be typed in.
The only number that may be added to the
sequence
7+9 and be divisible evenly by 9 is **2** (the digit I circled).
[7+9+2=18]
The designer has programmed the puzzle
to do the math so your computer has no problem supplying the 'missing'
number. |