Question

A chemical engineer is planning to start a starch manufacturing unit. He prepared a project plan, identified the activities and the expected time required for each activity. A project activity chart with expected time of all activities is given in the following table.

a. Draw the network diagram showing all activities as listed in the table.

b. Find out the critical path and earliest expected time duration for the project.

Activity	Time required (Hrs)	Predecessors
1	20
2	14	1, 3
3	12
4	14
5	20	3
6	10	2,4
7	8	5,6

Answer 1

a)

Activity	Activity	Earliest	Earliest	Latest	Latest	Slack
	Time	Start, ES	Finish, EF	Start, LS	Finish, LF	(LS-ES)
1	20	0	20	0	20	0
2	14	20	34	20	34	0
3	12	0	12	8	20	8
4	14	0	14	20	34	20
5	20	12	32	24	44	12
6	10	34	44	34	44	0
7	8	44	52	44	52	0

b)

Critical path includes the activities with zero slack.

So, critical path is 1-2-6-7 as shown by red circles in the above network.

Earliest completion time=time required to complete activities on critical path

=20+14+10+8=52 hours