Why do you think manholes are round in shape?
(You need to think a little crooked for this )
(In reply to re(5): A solution
Whether the triangle could fall through (or could be fitted through deliberately) would depend on the overall size of the triangle, the width of the lip (how much narrower the hole is than the cover) and the thickness of the cover. A triangular cover with side length of 36 inches would have an altitude of under 31.2 inches. The length of one side of the hole would be 36 - 2(√2) or over 32.5 inches, permitting the cover to fit through if it is presented as its altitude. Of course to allow for the thickness of the cover, we'd have to consider the portion of the hole even farther from the edge, which is even smaller, but that depends on the thickness of the cover. A larger than 36-inch side would allow greater thickness for the given lip width, and a smaller than 1-inch lip would also allow for a greater cover thickness.
Posted by Charlie
on 2003-02-21 04:49:40