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Topics: Scheduling
PDM
There are three tasks A, B, and C. C starts after two weeks of A completion and after B finished.What is the relation between A and B?

1) Finish to Start
2) Start to Finish
3) Start to Start
4) Finish to Finish
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Pooja

If I am not mistaken, this is a Finish to Start relationship because C can’t start before both A and B are complete. If no other conditions exist between A and B, it also creates a convergence node as the start of C is tied with the finish of both A and B with a lead time from A of two weeks.

RK
There is no information about the starts of A or B. Both need to finish before C can start (and A has a lag of 2 weeks for that).

So I would go with D, finish to finish.
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1 reply by Rami Kaibni
Jun 27, 2020 1:35 PM
Rami Kaibni
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Thomas

I have to disagree. If C cannot finish before A and B finish then that’s a Finish to Finish relationship but the situation is C can’t start before A and B finish so it’s a Finish to Start relationship.

Info about the start of A and B is irrelevant for what the situation is asking for.

RK
Jun 27, 2020 1:20 PM
Replying to Thomas Walenta
...
There is no information about the starts of A or B. Both need to finish before C can start (and A has a lag of 2 weeks for that).

So I would go with D, finish to finish.
Thomas

I have to disagree. If C cannot finish before A and B finish then that’s a Finish to Finish relationship but the situation is C can’t start before A and B finish so it’s a Finish to Start relationship.

Info about the start of A and B is irrelevant for what the situation is asking for.

RK
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1 reply by Thomas Walenta
Jun 27, 2020 1:55 PM
Thomas Walenta
...
Hi Rami,

it is a finish to start relationship between A and C as well B and C.
Between A and B it is not, but that is the question.

Thomas

Interesting.
Jun 27, 2020 1:35 PM
Replying to Rami Kaibni
...
Thomas

I have to disagree. If C cannot finish before A and B finish then that’s a Finish to Finish relationship but the situation is C can’t start before A and B finish so it’s a Finish to Start relationship.

Info about the start of A and B is irrelevant for what the situation is asking for.

RK
Hi Rami,

it is a finish to start relationship between A and C as well B and C.
Between A and B it is not, but that is the question.

Thomas

Interesting.
...
1 reply by Rami Kaibni
Jun 27, 2020 2:22 PM
Rami Kaibni
...
Thomas

I stand corrected, I totally missed that. For some reason I thought the question is asking about the relationship between C and (A/B).

The relationship between A and B given the current situation is a Finish to Finish because that is the only answer that makes sense given the info about the start of C. However, the question is a bit vague.

Thank you for correcting me.

RK
Rami Kaibni, I also gave the same answer as you mentioned but PMI goes with Thomas.

Thomas, I am still not clear why Finish to Finish is the answer when no information of A and B relationship is given. B can finish after A or A can finish after B or Both can start or finish at the same time.
Hi Pooja,

well, there is information given about A and B, though indirectly (both are predecessors of C). If you bring this together and since there is no information about the starts of either A or B, the only thing you can conclude is about the finishing of A and B.

It is not a perfect logical conclusion though. I did not succeed to find a f2f clause that describes their relationship without considering C. For example '
B has to finish when A finished plus 2 weeks' is not true.

But with any question, the correct answer could be the only one that is not plain wrong.

Thomas
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1 reply by Pooja Sharma
Jun 28, 2020 6:58 AM
Pooja Sharma
...
Thanks for your reply. Agree with your explanation.
Jun 27, 2020 1:55 PM
Replying to Thomas Walenta
...
Hi Rami,

it is a finish to start relationship between A and C as well B and C.
Between A and B it is not, but that is the question.

Thomas

Interesting.
Thomas

I stand corrected, I totally missed that. For some reason I thought the question is asking about the relationship between C and (A/B).

The relationship between A and B given the current situation is a Finish to Finish because that is the only answer that makes sense given the info about the start of C. However, the question is a bit vague.

Thank you for correcting me.

RK
Jun 27, 2020 2:19 PM
Replying to Thomas Walenta
...
Hi Pooja,

well, there is information given about A and B, though indirectly (both are predecessors of C). If you bring this together and since there is no information about the starts of either A or B, the only thing you can conclude is about the finishing of A and B.

It is not a perfect logical conclusion though. I did not succeed to find a f2f clause that describes their relationship without considering C. For example '
B has to finish when A finished plus 2 weeks' is not true.

But with any question, the correct answer could be the only one that is not plain wrong.

Thomas
Thanks for your reply. Agree with your explanation.

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