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 Covert Quantity II (Posted on 2013-08-20)
```+---------+-------+
| 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.

 See The Solution Submitted by K Sengupta Rating: 2.6667 (3 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
 Analytical solution (spoiler) Comment 3 of 3 |
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.

Next consider row 4.  Neither 4 nor 9 can be in the number.

Next. consider row 2.  We have already established that 1 and 9 are not in the number, so 8 is, but not as the 3rd digit.  The number must be 83?7.

Finally, look at row 1.  we have already established that 1, 5 and 9 are not in the number, so the last digit is 2.    The number is 8327.

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

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