***Activity Duration - Calculation ***


Activity 1 has a duration of 20 days, activity 2 of 10 days, activity 3 of 5 days and activity 4 of 6 days.

What is the minimum total duration between the milestones A and B?
 

  36 days
  37 days
  39 days
  42 days


 

 

Per my calculation - answer is 42 days. 

But correct answer is 37 days . 

Please advise.

 

 

Given: Activity 1 has a duration of 20 days, activity 2 of 10 days, activity 3 of 5 days and activity 4 of 6 days.


The calculation is as below:


Activity 3 is finish to finish.  Since the lead is two days.  The activity 3 will complete 2 days before activity 2.  Activity 4 will start after activity 3


=Activity 1 + Activity 2 - 2 days lead +  3days lag of activity4 + Activity 4 


=20 + 10 - 2 + 3+ 6


= 37 days.


 


 

Thanks for the details..

But my understanding is as follows:-

Activity 3 is finish to finish --> It means Activity 2 (Predecessor activity) should finish before finsh of successor activity ( Activity 3)

Since the Lead time for Activity 3 is 2 days , so Activity 3 can start 2 days before the finish date of Activity 2.

  

=Activity 1 + Activity 2+  Activity 3 with 2 days lead +  Activity4 with 3days lag

=20 + 10+ (5-2) + (6+3)

= 42 days.

 

Regards,

Sam

Activity 3 is finished 2 days early the finish of activity 2. =FF-2

Since Activity 4 is successor of activity 3 hence activity 4 will start 2 days early then activity 2 will get finish.

duration of activty 3 wil be thus not come in calculation.

20 (a1) + (10-2)(a2/a3) + 3 (LAG of a4) + 6 (a4) = 37

Thanks SSPawar and ShaikfromRiyadh

I have a doubt here.

Can we have the relation  FS -2 between Act 2 and Act 3 instead of FF - 2 ? then how the calculation would be?

 

 If its FS-2 then it shoudl be

20 + 10 + (5-2) + (6+3) = 42

Can you please interpet how your read this chart since this is the first time I have seen a PERT with FF.


Thanks

Which part of the question says that Activity 3 is FF

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what would be the result if it is SS-2 days between Activity 2 and activity 3.The same what it would be for SS+2 days.