ES – Early Start time, EF – Early Finish time
LS – Late Start time , LF – Late Finish time
Slack=LS-ES or Slack=LF-EF
Activities: A, B, C, D, E
Start date = date 0
Duration A = 12 days, Duration B = 10 days, Duration C = 10 days, Duration D = 5 days, Duration E = 3 days
Activities D and E go to FINISH. The time to complete the project is the highest of the EF times of the Predecessor nodes i.e. activities D and E cannot be completed in longer than 27 days. LF(E)=27.
Forward Pass: ES(C)=EF of Predecessor activities (largest)=12, EF(C)=ES+Duration of the activity=12+10=22
Backward Pass: LS(E)=27-3=24, LF(C)=LS of Successor activities (smallest)=22, LS(C)=LF- Duration=22-10=12
Slack(A)=0, Slack(B)=2, Slack(C)=0, Slack(D)=0, Slack (E)=2
Slack is the time an activity can be delayed without causing another activity to be delayed or impacting the completion date of the project.
The Critical Path is ACD.