Which pass computes the latest times (LS and LF) in a project network?

Which pass computes the latest times (LS and LF) in a project network?

• A. Forward Pass
• B. PERT
• C. Gantt Chart
• D. Backward Pass

Answer: (D)

The latest times in a project network come from the backward pass. After you’ve determined the earliest schedule with the forward pass, you look from the project’s end back toward the start to figure out how late each activity can finish and still meet the overall deadline. Start by setting the latest finish (LF) for the final activities equal to their earliest finish, which corresponds to the project duration. Then, for each predecessor, determine its latest finish as the smallest latest start among its successors: LF_i = min(LS of its successors). Once LF_i is known, you obtain the latest start as LS_i = LF_i − duration_i. This yields LS and LF values that show each activity’s freedom (slack) and identify the critical path where slack is zero. In contrast, the forward pass computes earliest start and finish times (ES/EF) and is used to build the initial schedule, while Gantt charts are visualization aids and PERT is a related planning method, not the calculation of the latest times.

The latest times in a project network come from the backward pass. After you’ve determined the earliest schedule with the forward pass, you look from the project’s end back toward the start to figure out how late each activity can finish and still meet the overall deadline. Start by setting the latest finish (LF) for the final activities equal to their earliest finish, which corresponds to the project duration. Then, for each predecessor, determine its latest finish as the smallest latest start among its successors: LF_i = min(LS of its successors). Once LF_i is known, you obtain the latest start as LS_i = LF_i − duration_i. This yields LS and LF values that show each activity’s freedom (slack) and identify the critical path where slack is zero.

In contrast, the forward pass computes earliest start and finish times (ES/EF) and is used to build the initial schedule, while Gantt charts are visualization aids and PERT is a related planning method, not the calculation of the latest times.