# Floats in the AoA network

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Floats in the AoA network
Project management (lecture)

Activity and event times
Activity times: EST LST EFT LFT Event times: EET LET

Float Time available for an activity or path in addition to its duration. It can be positive or negative It is a property of activities (and available only at given activities) In case of more succeeding activities, the minimum have to be taken. Types of float: Total float Free float

Total float 2 1 4 3 The total float possessed by an activity.
Calculation for activity j: Total floatj = LFTj – EFTj Identify the activity possessing float below, and calculate the total float. 2 ? 10 12 1 ? 4 ? 35 c a 15 3 ? 8 b d

Total float 2 1 4 3 The total float possessed by an activity.
Calculation for activity j: Total floatj = LFTj – EFTj = LFTj – (ESTj + Dj) Identify the activities possessing float below, and calculate the total float for each. Total float = = 11 – (0+5) = 6 2 5 Total float = 23 – (5+12) = 6 12 5 11 c a 1 4 23 15 8 23 b 3 15 d 15

Calculating free float
The float possessed by an activity which, if used, will not change the float in leater activities. Free floatj = ESTj+1 – EFTj = EEThead – EETtail - D Free float = = 5 – 0 – 5 = 0 2 5 Free float = 23 – 5 – 12 = 6 12 5 11 c a 1 4 23 15 8 23 b 3 15 d 15

Negative float If the target time (deadline) for the project (or for a part of the project) is grater than TPT, than the float will appear on the critical path or even on some other paths. Negative float = the time by which activities on the path or paths concerned must be reduced if the TPT is to be met. Negative float is a type of the Total Float. 30 1 ? 2 ? 3 ? 10 10 a c

Negative float If the tartget time (deadline) for the project (or for a part of the project) is grater than TPT, than the float will appear on the critical path or even on some other paths. Nagative float = the time by which activities on the path or paths concerned must be reduced if the TPT is to be met. Negative float is a type of the Total Float. 15 1 -5 2 10 5 3 20 15 10 10 a c Total float: -5 Total float: -5

Slack 2 1 4 3 Refers to events and not to activities.
Slack = LET - EET Slack: 6 Total float = = 11 – (0+5) = 6 5 Total float = 23 – (5+12) = 6 2 12 5 11 c a 1 4 23 15 8 23 b 3 15 d Slack: 0 Slack: 0 15 Slack: 0

Readings Lockyer – Gordon (2005) Chapter 13

Thanks for the attention!

2 7 10 7 11 c a 1 4 23 15 8 23 b 3 15 d 15

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