Use Pathagorean Theorem to solve (right triangle with the base being one of the side lengths and the height being the other side length. a^2 + b^2 = c^2
64^2 + 100^2 = length of diagonal ^2
4096 + 10000 = 14096
The length of the diagonal is the square root of 14096 or 118.727 meters (rounded to the thousandths place).