#15 Lines through the chessboard
Linus is using a thin felt-tip pen and a ruler to draw straight lines on a conventional 8×8 chessboard. With eight lines, he can easily ensure that a line passes through every square on the board. For instance, he can just draw a line through the middle of each row of squares, which means each line would go through eight squares. But a line can pass through more than eight squares – for example, the one in the illustration goes through nine – so Linus wants to find a way to cut through all 64 squares with fewer than eight…
