Critical Path and PERT

1) A PERT project has 45 activities, 19 of which are on the critical path. The estimated time for the critical path is 120 days. The sum of all activity variances is 64, while the sum of variances along the critical path is 36. The probability that the project can be completed between days 108 and 120 is

a) 0 -2.00
b) 0.0227
c) 0.1058
d) 0.4773
e) 0.9773

2) A project being analyzed by PERT has 38 activities, 16 of which are on the critical path. If the estimated time along the critical path is 90 days with a project variance of 25, the probability that the project will be completed in 88 days or less is

a) 0.0228
b) 0.3446
c) 0.6554
d) 0.9772
e) 18

3) Analysis of a PERT problem shows the estimated time for the critical path to be 108 days with a variance of 64. There is a .90 probability that the project will be completed before approximately day ________.

a) 98
b) 108
c) 109
d) 115
e) 118