PK0-005 Project Life Cycle Practice Question
A project has a critical path duration of 45 days. Activity X on the critical path has an optimistic duration of 5 days, a pessimistic duration of 13 days, and a most likely duration of 8 days. What is the expected duration of activity X using PERT?
⚠ Common exam trap
The trap is using the simple average (O + M + P)/3 instead of the PERT weighted formula (O + 4M + P)/6, or mistaking the most likely value for the expected duration.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
8.33 days
PERT uses the weighted average formula Expected = (Optimistic + 4 × Most Likely + Pessimistic) / 6. Plugging in O=5, M=8, P=13 gives (5 + 32 + 13) / 6 = 50 / 6 ≈ 8.33 days. This beta-distribution weighting emphasizes the most likely value while accounting for uncertainty.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
8.0 days
Why it's wrong here
PERT weights the most likely estimate fourfold, giving (5 + 4×8 + 13) ÷ 6 = 50 ÷ 6 ≈ 8.33 days, not 8.0. The simple average of the three estimates, 8.67 days, is also wrong; 8.0 would only be correct if the most likely value alone were used.
- ✓
8.33 days
Why this is correct
PERT weights the most likely estimate four times: (5 + 4×8 + 13) ÷ 6 = 50 ÷ 6 = 8.33 days. This expected duration replaces the single-point estimate for activity X on the critical path.
- ✗
7.5 days
Why it's wrong here
PERT weights the most likely estimate fourfold: (5 + 4×8 + 13) ÷ 6 ≈ 8.3 days. The 7.5 figure comes from an unweighted mean of the three estimates, which suits a triangular distribution rather than the beta distribution PERT specifies.
- ✗
9.0 days
Why it's wrong here
PERT weights the most likely estimate fourfold: (5 + 4×8 + 13) ÷ 6 = 50 ÷ 6 ≈ 8.3 days. The 9.0 figure arises from wrongly applying a simple three-point average or rounding error, ignoring the beta distribution weighting that PERT mandates.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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