The project manager has following information about duration for an activity: Most likely [tM] - 15 days Pessimistic [tP] - 20 days Optimistic [tO] - 10 days What is the estimated duration of this act

10 days is the optimistic estimate (tO) alone and is not the result of applying any three-point estimation formula combining all three input values.

The triangular distribution formula is (tO + tM + tP) / 3 = (10 + 15 + 20) / 3 = 45 / 3 = 15 days. Unlike the PERT beta distribution formula - (tO + 4tM + tP) / 6 - which weights the most likely estimate four times, the triangular distribution treats all three estimates equally as a simple arithmetic mean, producing 15 days in this case.

12.5 days does not result from any standard three-point estimation formula - neither triangular nor PERT beta - applied to the given values of 10, 15, and 20.

5 days represents the difference between the optimistic and most likely estimates and has no basis as a duration estimate under any recognized three-point distribution technique.