106. Given this portion of the network diagram to the right,
what’s the LF of activity F?
A. 10
B. 11
C. 16
D. 17

( not able to attach the picture)

It’s just easy to calculate the late finish (LF) of an activity in a network diagram. Look at the
following activity, take its LS (late start), and subtract one. If there’s more than one following activity,
use the one with the lowest LS. So for activity F in the question, the following activities are G, with
an LS of 17, and H, with an LS of 11. So the LF of F is 11 - 1 = 10.

As per Rita Book , we do not have to do LS(predecessor)  = LF(successor) - 1 , just LF of predecessor activity will become LS of successor.

Regards,
Sam

### ***Correction

106. Given this portion of the network diagram to the right,
what’s the LF of activity F?
A.  10
B.  11
C.  16
D.  17

( not able to attach the picture)

It’s just easy to calculate the late finish (LF) of an activity in a network diagram. Look at the
following activity, take its LS (late start), and subtract one. If there’s more than one following activity,
use the one with the lowest LS. So for activity F in the question, the following activities are G, with
an LS of 17, and H, with an LS of 11. So the LF of F is 11 - 1 = 10.

Correction

As per Rita Book , we do not have to do LF(predecessor)  = LS(successor) - 1 , just LS of successor activity will become LF of predecessor.

Regards,
Sam

### how can i answer this if

how can i answer this if there is no graph?

Graph @ http://www.headfirstlabs.com/books/hfpmp/hfpmp_ch15.pdf  --> 106 Question....

I am also interested in knowing - in general what is rule to get the LF of the activity ?

### 10 is correct

successor activities are 2 , one have LS = 11, other have 16.

hence activity F should have to finish 1 day/week/hour (what ever be the unit) ahead evening or so. To give late start  one of successor on 11, activity F will take late finish on 10.

its so simple, i dont think you should follow any memorised funda, better develop self concept and sense of judgement.

Regards

### Right SSpawar , but per Rita book....

You are right its very simple and straight but per Rita Book (7th edition)- Page No 199 and 200 , there is no substraction of 1 day...hence I am confused..

### Sam,This question also

Sam,

This question also caught me by surprise becaue if you take any node (say D for example) and subtract from ES from EF it will give 2 as the duration but if you subtract LS from LF it gives 1 as the duration so I did not get whats going on.

As far as comparing it with Rita page 200 is concerned , she does not subtract 1 .Understand that end of the day and morning of the following morning refre to  the same thing.

So I guess we need to understand the scenario and how the diagram has been refered and we can not simply memorize whether to memorize or not memorize the formula as it is.

Also here I would like to know everyone's opinion about Head First's questions quality of the questions.  I scored 83% in this so what should I make out of this.

Thanks,

PN

### i think there should be some standard rule...

Choices have both options 10 and 11.....and looks like its completely on assumption , successor activity can  start same day or next day and these assumptions will lead to different answers...

Can anyone please throw some light on this scenerio and guide on which way to go ?

Regards..Sam

### Sam, thanks i already saw the

Sam, thanks i already saw the question and the graph. Here is my analysis and conclusion.

1. The network is erroneous. If you look at Activity D, the duration is 2 - can be derived by EF - ES; 9-7 = 2; This should be the same by also using LF-LS; but LF=4, LS=3, meaning 4-3 = 1; it must also be 2. If you will see Activity H, the values are consistent, the duration is 2 both by using EF-ES and LF-LS. There is no other condition in the question that would give explanation why the method of calculation in Activities D and E is different than Activities G & H.

2. In that network diagram the LF of Activity F must be the LS of the lowest succeeding activity (since there are more than one successor, and that must be 11 (LS of Activity H.

Therefore, my conclusion is: The answer and explanatiion to that question is WRONG. As what you said, Rita's explanation is the same as what i am explaining. I totally agree with Rita. And you also refer to other explanations or other explanations related to CPM, they would have the same explanation as i am and rita.

Please take note also that in a CPM, we dont consider a lag of EVENING (as pointed out by sspawar), unless probably in some situation where a lag is clearly specified.

I want to share this video lesson on how to deal with network diagram. May this be helpful. I advice to forget that question and explanation from Headfirst, i dont know from which theory they got that :)

Here is the link to the short video tutorial.  http://www.pmptrend.com/index.php/en/forum/3-Suggestion-Box/85-Project-Management-Network-Video-Lessons#85

### Great Explanation !!

Thanks Projmanpro...great explanation...I got it....

### In my understanding

In my understanding Headfirst and Rita and others and me all are talking on the same line.

It happens sometimes, for a while we get confused but the way you can understand better and want to come to the true result, is the best for you.

while reading question many gold plated or unnecessary stuff will be there, but we have to screen and give weightage the required one.

Regards

### dude how can u say u,

dude how can u say u, headfirst and rita and others are talking about the same line, obviously, you and headfirst talk about subtracting 1 from the lowest LS of the successor to get the LF of the predecessor, while Rita and me and maybe others are talking against it.

so are u saying that in "backward pass", 1 must be subtracted? well it is up to you, i respect your understanding.

How ever procedures methods,ways may be different but if logically they are correct and reached to the answer then it have same understanding and knowledge.

In Rita , presentation way is the same as MS Pro, and it is different from headfirst. It is way of presentation but the ultimate meaning is same.

for example if I say 3+1 =4 and u say no 1+3 = 4, it is like that.

As per Rita or MSpro - if any activity start on 20 and finish on 20, you will write ES of LS = 19, this is logic they adapt.

So it is sense of judgement, in that perspective headfirst is wrong, but there is no such hard and fast rule.

You have to just keep understanding clear by observing the way it is represented.

http://www.pmhelpdesk.com/entries/20346821-why-are-there-two-methods-for-calculating-es-ef-ls-and-lf

http://www.wiziq.com/tutorial/161227-Most-updated-Project-Time-Management-Process

Regards

### who told u that PMP

Who told u that PMP recommeds that? why should a pmp recommend a process that has more complexities if there is another simplier yet correct process?

Second, ur argument is again outside of the subject of the question. I emphasized earlier that the question's diagram is full of confusion, i concluded it as wrong. So why are u trying to justify the question? IF U ARE SAYING THAT WHICHEVER PROCESS IS USED WOULD GIVE THE SAME ANSWER THEN HOW COME ANSWERS WOULD BE 10 IF SUBTRACTED while 11 if not and both must be correct? Tsk tsk.

Headfirst is following method 2 of that link, while Rita following 1.

This confusion is all because of this.

Later things will be clear as a crystal.

Still if you say no 11 is wrongly written in head first, then I have no argue with you this is for others.

Regards

### till now dude u dont get my

till now dude u dont get my point. i want u to go back to the network diagram provided by headfirst in that sample question. other nodes shows consistent info, say in terms of duration as calculated by EF-ES or LF-LS, while in some nodes are not consistent. If only there is consistencies in that diagram, then both methods applied and will give the same result, AND I AM SURE THIS POST WILL NOT BE POSTED HERE.

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