Critical Paths - help??

[shinymeowstic]

Hello!!

I really struggle to figure out critical paths, and overall, I have a LOT of trouble with everything to do with 'The Critical Path Problem', I have trouble drawing them from a table, and adding extra paths, etc. Please, any advice on this would be really useful as I'm really strugging!!
For the 2013 exam no 2, question 2 in Networks, how do you go about doing it?

[plato]

You had to draw in G. Its predecessors were B, D and H and these three all ponted to one vertex. This is where G starts.
Now look for any activities that have G as a predecessor. Activity I cannot start until G is complete and so G stops wher I starts.

Maybe the following could get you started on finding a critical path.
From the start, follow each activity to a vertex where another activity will start. Mark the earliest starting time (EST) at that vertex of the next activity. For instance, the EST for F is 5 'cos it took 5 hours for activity A to finish.

Follow F along to give the EST of I is 20; calculated from the time for A plus the time for F. Follow I along to give the EST of M is 29.

If you had first followed activity B from the start, it would have appeared that the path BJK gives an earlier starting time for M of 19. Eventually you would have followed activity A and found that can still not start until activity I has been completed. The EST of M is 29.

It follows that the earliest that M could finish is 29+8=37 hours.

Do this for every path leading to every vertex. Then look at the longest of these paths from start to finish. That is your critical path which, in 2013, was AFIM.