+---------+-------+
| 1 2 5 9 | R     |       
+---------+-------+       
| 1 3 8 9 | R B   |     
+---------+-------+        
| 1 3 5 7 | B B   |        
+---------+-------+     
| 4 3 9 7 | B B   |        
+---------+-------+

Each of the rows in the table given above indicates an attempt to find out the secret number. Each try has, in the column to the right, the letters R and B.

Each R indicates that this number has one digit in common with the secret number, but in a different position.

Each B indicates that this number has one digit in common with the secret number in the same position.

Determine the secret number.

Consider rows 1 and 3.  The one hit in the first row is in the wrong position, but the two in the 3rd row are in the right position. Therefore, neither 1 nor 5 can be in the number.  Therefore, the number must be ?3?7.

Posted by Steve Herman on 2013-08-20 19:14:49