Question

A project is represented by the activity duration (in days, estimated at 90% likelihood of completion) and precedence requirements shown in the table. How many feeder buffers are needed if this project is managed using critical chain methodology?

Activity	Predecessor	Length	Activity	Predecessor	Length
A	--	18	E	C, D	13
B	--	16	F	C	9
C	A	22	G	E, F	15
D	B	14	​	​	​

Options:

0

1

2

3

Answer 1

The activity table is:

Activity	Predecessor	Length
A	---	18
B	---	16
C	A	22
D	B	14
E	C, D	13
F	C	9
G	E, F	15

The precedence diagram is:

The critical path is the path with the longest total task length.

Length of each path is:

A -> C -> F -> G: 64

A -> C -> E -> G: 68

B -> D -> E -> G: 58

Hence, the critical path is A -> C -> E -> G

Feeding buffer (or feeder buffers) are used in the non-critical paths so that any delay in the non-critical path wont delay the critical path.

Here the critical path is A->C->E->G

This path depends on B->D->E->G non-critical path so as to start E on time.

This path depends on A->C->F->G non-critical path so as to start G on time.

As the likelihood of completion is 90%, hence 90% of the total task time should be performed. 90% of total task time is = 0.9*107 = 96.3

Hence till the starting of task G, it should be completed.

Hence, the number of feeder buffers used = 2.

Answer is: 2

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