In a 3x3 grid, what is the top-left value after a horizontal reflection of the standard arrangement 1 2 3 / 4 5 6 / 7 8 9?

In a 3x3 grid, what is the top-left value after a horizontal reflection of the standard arrangement 1 2 3 / 4 5 6 / 7 8 9?

• A. 7
• B. 3
• C. 1
• D. 9

Answer: (B)

Flipping left and right in each row moves the leftmost value to the right end and the rightmost value to the left. In the top row, 1 2 3 becomes 3 2 1 after this horizontal (left-right) reflection, so the top-left position now holds the original top-right value, which is 3. If it were a flip across a horizontal line, the top-left would instead become 7, but the intended reflection here yields 3.

Flipping left and right in each row moves the leftmost value to the right end and the rightmost value to the left. In the top row, 1 2 3 becomes 3 2 1 after this horizontal (left-right) reflection, so the top-left position now holds the original top-right value, which is 3. If it were a flip across a horizontal line, the top-left would instead become 7, but the intended reflection here yields 3.