# What is the duration of this activity?

1.       An activity has an early start,(ES) of day 13,an early finish (EF) of day 9 and a late finish (LF) of day 19. What is the duration of this activity?

A 3

B 6

C 7

D 10

I'm guessing there is typo in the question how can ES be 13 and EF be only 9?

### Its not typo.They want make

Its not typo.

They want make confuse us.  They ask only duration na, simple do LF-LS

i.e 10

### there is no LF value in that question. only ES & EF is given.

There is no LF..only LS is given.

based on the question .. the duration is -4 (EF-ES)

but the answer is not available ??

### typo also in my reply.They

They want make confuse us.    They asl only duration na, simple LF-LS or EF-ES.

i.e 6  ( 10 is the float)

### 10 is free float value not a activity duration.

<p>LF-EF / LS-ES is free float formula.. Whereas EF-ES is the duration formula.&nbsp;</p><p>&nbsp;</p><p>please correct me if iam wrong.&nbsp;</p><p>&nbsp;</p>

### 10 is free float value not a activity duration.

LF-EF / LS-ES is free float formula.. Whereas EF-ES is the duration formula.

please correct me if iam wrong.

### Some problem in this question for sure

Yes keyveeyen  equations are correct.

LS-ES or LF-EF give the float of the activitity

EF-ES or LF-LS give the duration of the activity

As per the given values float is 10 and duration is -4 (How can -4 be the duration of an activity?)

### @JP2786While cut and paste

@JP2786

While cut and paste somebody missed some information somewhere in some website.  Thats why this mistake may conitues for one website onother one.   I searched in the google.  I found this information.  I concludes that the right version of the question may be as follows:

An activity has an early start (ES) of day 3, a late start (LS) of day 13, an early finish (EF) of day 9, and a late finish (LF) of day 19. What is the duration of this activity?

a. 3
b. 6
c. 7
d. 10

Here answer is C. 7 days.

### Yup

Looks like thats the correct version. Thanks for posting.

Hi Guys,

As per the above Q : EF-ES or LF-LS = 6. So B should be right one.

### ES=3 and EF=9

ES=3 and EF=9

Duration of days = 3,4,5,6,7,8,9 = Seven days
Duration Formula = EF-ES+1

of day 3, a late start (LS) of day 13, an early finish (EF) of day 9, and a late finish (LF) of day 19. What is the duration of this activity?

a. 3
b. 6
c. 7
d. 10
Here answer is C. 7 days.

### @typo

@typo

ES=3 and EF=9 Duration of days = 3,4,5,6,7,8,9 = Seven days Duration
Formula = EF-ES+1

### Thanks for the clarification

Thanks Sunku65 for the clarification.

### why do duration formula is

why do duration formula is sometime calculated as
duration = ES- EF

and sometime as
duration = ES- EF+1

Please explain.when do we prefer which formula.

### Its for our convenience:

Its for our convenience:
Some times network diagram starts with ES=0 or ES=1

Example: A=3 days; B=5 days; C=2days
Path = Start-A(FS)-B(FS)-C(FS)-End
Duration = 3+5+2 =10 days

RITA follows below method :

First activity(A) successor of Start :
ES=0
EF =ES Duration=0+3= 3.

Activity B:
ES =Predecessor Activity A's EF becomes successor activity ES. ie. ES=3.
EF=ES Duration = 3+5=8

Activity C:
ES =Predecessor Activity B's EF becomes successor activity ES. ie. ES=8..
EF=ES Duration = 8+2=10

WE follows below method :

First activity(A) successor of Start :
ES=1
EF =ES Duration-1=1+3-1= 3.

Activity B:
ES =Next day of Predecessor Activity A EF becomes successor activity ES; i.e. ES = 4
EF=ES Duration-1 = 4+5-1=8

Activity C:
ES =Next day of Predecessor Activity B EF becomes successor activity ES;
i.e ES=9.
EF=ES Duration-1 = 9+2-1=10

Depending on given network diagram.
If network diagram starts with 0 as ES, then apply 1st one.
else network diagram starts with 1 as ES, then apply 2nd one

If anything wrong correct me.
Thanks,
Lax