Question- total duration b/w activities


Found this question on Oliver. Can someone pls explain.

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




Act Dur

Calendar days Assuming Act1 start day as 1st  

#Days in to the calendar

Acitvity 1

Act 1 can be started after reaching Mile stone A (FS)

20 d

1st to 20th


Acitvity 2

Act 2 can be started after Act1 is finished (FS)

10 d

21st to 30th


Acitvity 3

Act 3 can be finished 2 days before Act2  is finished (FF -2days)

5 d

Any 5 days between 21st & 28th


Acitvity 4

Act 4 can be started 3 days after Act3 is finished (FS+3)

6 d

29th to 31th idle days.
Activity4 will be from 32nd to 37th



37 days

 Note:    Activity 3 is done in parallel with Activity 2 & getting finished before activity 2

Vijay Bheemineni, MS, PMP, ITIL.

Thanks again Vijay..

Kaam_wali_Bai's picture


Why do we need to take  [-2] in account while calculating duration of activity 4? Activity 3 can be finished together with activity 2 and has 0 duration. Then all we have is FF+3 which will result in [6+3 =9] for activity 4

Activity A 


0                                              19                    = 20 days

Activity B


20                                           29                   =  10 days


Activity C


25                                          29                     = 0 days


Activity 4  [ 30,31,31 for lag time of 3]

<------------------------------------->                   = 3 days of leg + 6 days = 9 days

33                                            38

so total should be 39?

Can someone help here?

You have missed FF -2 for activity 3

Kaam_wali_Bai's picture

Why should I take FF-2 for Activity 3 into account when it is done in parallel with Activity 2?

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