The chessboard is about 26.4 centimeters long. to find the answer you need to know the length of one side of a square, which is about 3.3 centimeters, because the area is 11, so the square root of 11 is about 3.3 centimeters. there are 8 squares, so you have to multiply 8 times 3.3 which equals 26.4.
