Which of the following is associated with a critical activity in an A-O-A network?
- AMaximum Float.
- BMinimum Float.
- CZero Float.Correct
- DFree Float.
Solution
Concept
A critical activity is an activity on the longest path of a project network. Any delay in this activity delays the entire project, so it has zero float.
Formula
Total Float = 0 (for a critical activity)
Step-by-step solution
1. In an Activity-on-Arrow (A-O-A) network, 'float' means extra time available to complete an activity without delaying the project. 2. A critical path is the longest duration path through the network. 3. Activities along this critical path are called critical activities. 4. Since critical activities cannot be delayed without delaying the whole project, they have zero total float. Answer: (C) Zero Float.
Explanation
Float is the spare time available for an activity. A critical activity has no spare time at all. Therefore, a critical activity always has zero float.
Why the other options are wrong
A: Critical activities have no extra time, so float cannot be maximum. B: 'Zero float' is the specific and standard defining condition for critical activities. D: Free float is float that affects only succeeding activities; critical activities have zero free float as well.
Shortcut
Critical means no delay allowed, so float must be zero.
Common mistake
Students sometimes choose minimum float because in rare cases with target deadlines float can be negative, but standard critical activities by definition have zero float.
Correct answer: C) Zero Float.