Question 139
The numbers $1, 2, \dots, 25$ are written in the cells of a $5 \times 5$ grid as shown below.
Is it possible to make all the numbers in the grid equal by performing a series of operations, where each operation consists of selecting any $3 \times 1$ or $1 \times 3$ subgrid and incrementing each number in the selected subgrid by 1?
Is it possible to make all the numbers in the grid equal by performing a series of operations, where each operation consists of selecting any $3 \times 1$ or $1 \times 3$ subgrid and incrementing each number in the selected subgrid by 1?