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Durations on PERT charts

Look carefully at this table which shows the sequence of tasks in building a brick fence and the duration of each of the tasks.

  Task Nodes Duration (days)
A Make enquiries and order all materials required 1 2
B Wait for bricks, sand and cement to arrive 2 2
C Clear the site 2 3
D Order concrete to be delivered 2 1
E Dig the trench 4 2
F Pour the footings 5 2
G Footings curing time 6 3
H Load the bricks on the site 3 3
I Mix the mortar and lay the bricks 7 1
J Clean the area 8 1
  Finish 9  

When these times are added to the activity arrows on the PERT chart, an overview of the total job time is given.

From node 1, the first task is 'Enquiries, orders'. Node 2 has three branches, one to 'Wait bricks' which leads to node 3 'Load bricks' then on to node 7. Also from node 2 is 'Clear site' then node 4, 'Dig trench' then node 5. The third task from node 2 is 'Order concrete' which also joins to node 5. The next task is 'Pour footings' then node 6, 'Footings curing' then node 7. The final section of the chart is 'Mix mortar & lay bricks' then node 8, 'Clean up' then the final node number 9. Duration times for these are given in the table.

Note that there are several pathways through the network, depending on which activity you choose to follow through.