How do total float and free float differ in CPM scheduling?

How do total float and free float differ in CPM scheduling?

• A. Total float and free float are the same concept used for schedule margins.
• B. Total float is the time an activity can be delayed without delaying the project finish; free float is the time an activity can be delayed without delaying its successor.
• C. Total float is the time an activity can be delayed without affecting the project start.
• D. Total float is the time an activity can be advanced; free float is the time it can be delayed.

Answer: (B)

Float in CPM scheduling is the amount of delay an activity can incur without pushing the overall project schedule out of the planned finish date. There are two forms, and they look at different constraints along the network. Total float refers to how long an activity can be delayed without delaying the project finish date. It captures all downstream effects on the project as a whole. Free float, on the other hand, is the delay allowance for that activity specifically without delaying its immediate successor. In other words, you can push an activity back some amount without affecting the start of the next task, but that same delay might still ripple further down and affect the project finish if the downstream path tightens. For clarity, imagine an activity finishes at time 5 and has a latest finish at 8, giving a total float of 3 days. If the next activity can’t start until time 7, you can delay the first activity by up to 2 days without delaying the next one (free float = 2). You could delay it up to 3 days without delaying the project finish (total float = 3). If the next activity’s start is already constrained to 5, the free float would be 0, even though the total float might still be positive if later tasks allow slack. So the best choice is that total float is the permissible delay without delaying the project finish, while free float is the permissible delay without delaying the downstream successor.

Float in CPM scheduling is the amount of delay an activity can incur without pushing the overall project schedule out of the planned finish date. There are two forms, and they look at different constraints along the network.

Total float refers to how long an activity can be delayed without delaying the project finish date. It captures all downstream effects on the project as a whole. Free float, on the other hand, is the delay allowance for that activity specifically without delaying its immediate successor. In other words, you can push an activity back some amount without affecting the start of the next task, but that same delay might still ripple further down and affect the project finish if the downstream path tightens.

For clarity, imagine an activity finishes at time 5 and has a latest finish at 8, giving a total float of 3 days. If the next activity can’t start until time 7, you can delay the first activity by up to 2 days without delaying the next one (free float = 2). You could delay it up to 3 days without delaying the project finish (total float = 3). If the next activity’s start is already constrained to 5, the free float would be 0, even though the total float might still be positive if later tasks allow slack.

So the best choice is that total float is the permissible delay without delaying the project finish, while free float is the permissible delay without delaying the downstream successor.