- Hieu
- Aug 22
- 2 min read
Updated: 2 days ago
Crack a 3x3 grid passcode!
Answer
Explanation
From grid 1, 4 numbers are in the correct column but wrong row
=> 6, 7, 2, and 3 are all in the correct column
We’ll focus on the fact that 6 is in the first column
Grid 2 says that “1 number is in the correct column, but wrong row and 3 numbers are in the correct row but wrong column”. We see grid 2 has 6 in the first column and that’s the correct column according to grid 1. Therefore, 6 must be the “1 number is in the correct column, but wrong row“. Meanwhile 4,1, and 9 are in the correct row, but wrong column.
In grid 1, we know 6 is in the wrong row and it’s written on R3
=> 6 is not in R3
In grid 2, we know 6 is in the wrong row and it’s written on R2
=> 6 is not in R2
=> 6 must be in R1
According to Grid 2, 4 and 1 are in the correct row but wrong column
=> 4 and 1 are in R1 but in a different order
We also know for sure that 6 is in C1R1
=> The only possible order is 6, 1, 4
We know 7 is in the correct column but wrong row (Grid 1)
=> 7 is in C2 but not R2
However, R1 is already filled with 3 numbers (6, 1, 4)
=> 7 must be on C2R3
From Grid 1, we know 2 and 3 are in the correct column but wrong row
=> 2 and 3 are both on C3
2 is not in R1
3 is not in R3
On the other hand, R1 is taken by 4 => 3 must be in R2 => 2 is in R3
Moving on to Grid 3, we have “1 number is in the correct column but wrong row”
If that number was:
5 => impossible, C3 has been fully filled
9 => impossible, C3 has been fully filled
4 => impossible, we know 4 is in C3R1
=> Must be 8.
=> 8 is in C1 but not R1
=> 5, 9 (and 4 but we already know 4’s position so this doesn’t matter) are in the wrong row and wrong column (Grid 3's second clue)
Focus on the number 5. It cannot be on R1 and C3 => The only remaining slot is C1R1
=> 8 is in C1 so only position is C1R2
That leaves 9 as the final final number, which is placed in the middle.
Free talk
(Dad joke) Why is isopropylbenzene smart?
Answer
Because it is a-cumen
Check out Vietnamese version for another dad joke :D
Alright so I made quite a few mistakes with this puzzle. I fixed the one sent to me by NMinh, which then poked another hole in the reasoning process and lead to an extra solution (discovered by a guest). I can just leave it there and say there are two answers, but that would be kinda lame and lazy. Now, I've changed the puzzle again and it should only have one solution. However, if you find another, please leave a comment about it!
new explanation soon...
Why is this not an answer?
814
973
652
Some problems with the puzzle but this's a good one~