Diagonal method

Imagine you have a big grid that looks like a checkerboard. Each little square is either black or white. Now, if you want to find out if the total number of black squares is equal to the total number of white squares in the whole grid, you can use the diagonal method.

Here's how it works: start by drawing a diagonal line across the grid, from the top left corner to the bottom right corner. Count how many black squares are on the top left of the line and how many white squares are on the bottom right of the line. Then, do the same thing but draw a diagonal line from the top right corner to the bottom left corner. Count how many black squares are on the top right of the line and how many white squares are on the bottom left of the line.

If the number of black squares on the top left of the first line is the same as the number of white squares on the bottom right of the first line, and if the number of black squares on the top right of the second line is the same as the number of white squares on the bottom left of the second line, you can conclude that the total number of black squares is equal to the total number of white squares in the whole grid.

So basically, by dividing the grid diagonally into two parts, you can check if they both have the same number of black and white squares. It's like cutting a cake in half and making sure each piece is the same size!