Why is pert equation divided by 6?

Answer 1

The Pert equation: (O+4M+P)/6, is basically a weighted average used to estimate a value.

O= Optimistic (best) value

M= Most likely value; multiplied by 4 because it is more likely.

P = pessimistic (worst) value

An average is the sum of a group of numbers divided by the count in the group. If we look at the Per Equation as: (O+4M+P)/6 = (O+M+M+M+M+P)/6, you can see the six items that are being averaged.