3x3 Magic Square Grid Entry

The sum of numbers 1 to 9 is 45. Since there are 3 rows/columns, each row/column/diagonal sum is $45 / 3 = 15$.

Let the grid be:

6  a  2
b  c  d
e  f  g

Top row sum: $6 + a + 2 = 15 \implies a = 7$.

In a standard 3x3 magic square with 1 to 9, the middle entry $c$ must be 5.

Let's check diagonals and rows:

• Top-right to bottom-left diagonal: $2 + c + e = 15 \implies 2 + 5 + e = 15 \implies e = 8$.
• Top-left to bottom-right diagonal: $6 + c + g = 15 \implies 6 + 5 + g = 15 \implies g = 4$.
• Left column: $6 + b + e = 15 \implies 6 + b + 8 = 15 \implies b = 1$.
• Right column: $2 + d + 4 = 15 \implies d = 9$.
• Bottom row: $e + f + g = 15 \implies 8 + f + 4 = 15 \implies f = 3$.

Thus, the bottom middle entry $f$ is 3.