Crack a 3x3 grid passcode!

Puzzle 22 Firewall Breach.pdf

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Answer

Explanation

*Rows and columns are counted left to right, top to bottom. R=Row, C=Column.

For example, R1=1st Row, C1= 1st Column.

Highly recommend opening two tabs side-by-side to view both the explanation and the puzzle's diagrams at the same time.

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 C1

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 C3 and R2 => The only remaining slot is C1R3

=> 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 (nerd alert): Why is isopropylbenzene smart?

Answer

Because it is a-cumen

Check out Vietnamese version for another dad joke :D