Oliver Lehmann - 75Q: Float calculation
Submitted by savian on Mon, 10/25/2010 - 07:34
Hi all,
There's something I'm a little confused about on question 18 from this test:
| 18. | Start dates in the following network logic diagram are defined as early morning, finish dates are evening. If tasks are scheduled to begin at early start date, what is true?
| |
| Activity B has a free float of 10 d. | ||
| Activity B has a total float of 10 d. | ||
| Activity A has a free float of 10 d. | ||
| Activity A has a total float of 10 d. | ||
Total float = LS - ES = (Day 21 - Day 16) = 10 days
Free float = ES of successor - EF of current task = (Day 31 - Day 21) = 10 days
Did I miss something out here? This question has 2 answers?
Forums:
raj9
Thu, 10/28/2010 - 17:07
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B
Correct answer is B.There are no two answers.
Free Float- The amount of time an activity can be delayed without delaying the early start date of its successors.
If you delay activity B by 10 days(using total float) it finishes on day 31, which is ES of activity D.Hence you can start activity D on day 32.
Free float is ES of successor minus late finish of current task.
Raj
gjc
Fri, 01/07/2011 - 16:42
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Total Float of B is (LF - EF)
Total Float of B is (LF - EF) or (LS - ES) = (31 - 21) or (26 -16) = 10 days
Free Float is (ES of successor - EF of current task - 1) = (31 - 21 - 1) = 9 days.
I've also seen Free Float calculated as (ES of successor - ES of current task - duration of current task)
Duration of B is (EF - ES + 1) = 21 - 16 + 1 = 6 days
Therefore Free Float of B = (31 - 16 - 6) = 9 days.
Be careful though, I have seen schedule diagrams where the EF of current activity and ES of successor activity are the same day. You need to understand the concepts to be able to adjust the formulas accordingly.
matteo_toniolo
Tue, 11/19/2013 - 22:54
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VERY SIMPLE IF YOU USE YOUR FINGERS
The formulas are still the same:
free float = ES (of successor) - EF (predecessor)
total float = LF-EF or LS -ES
Free float:
Day 31 is when Activity D starts, so that is not a day to count. You count with your hands: 30 (useful day to do things), 29, 28, 27, 26, 25, 24, 23, 22 and that is it, because 21 is already used. So how many days? 9
Total float:
Ok so day 31 is LF and day 21 is EF: how many days do we have: 21 no because it is already used. So then 22, 23, 24, 25, 26, 27, 28, 29, 30, 31. Yes also 31 because we use also the day 31 to perform the activity. How many in total? count: 10.