Question

Activities A, B, C and D from the critical path for a project with a PERT network. The means and variances of the activity duration for each activity are given below. All activity durations follow the Gaussian (normal) distribution, and are independent of each other.

Activity	A	B	C	D
Mean (days)	6	11	8	15
Variance (days${}^2$)	4	9	4	9

The probability that the project will be completed within 40 days is ____. [Round off to two decimal places]

[Note: Probability is a number between 0 and 1]

• A. 50

Answer 1

The correct option is A 50
$\text{PERT - CPM}$

$T_S=40\text{days,}{T}_E=6+11+8+15$

$T_E=40\text{days,}$

$2=\frac{T_S-T_E}{\sigma }=0\to 50\text{\%}$


$\text{Probability of completing project in expected time is always 50\%.}$