Weight calculation error behind Tokyo construction site accident

See my old teacher Mr. Gibbs was right. Math is important.

A very sad and avoidable accident led to the deaths of two workers.

Mistakes happen, construction work has always been hazardous. Get it right, make it right, and move on !

There must be a big engineering mistake in the weight calculations. They are supposed to hava a factor of safety to handle more weight than the total weight of the material.