CIMA E2 Syllabus C. Managing projects - LET - Notes ^{7 / 16}

Latest event time (LET) is entered in the lower-right quadrant of each event circle. This can be explained by the latest time that this project can be finished by. Here we work backwards (right to left) and we start at Event 7.

Therefore, using our ‘Example Above’ (EA) the latest it can be finished by is 23 which is the total duration of the project.

We will calculate LET for each event in the following way:

At Event 6, the latest event time is: Total duration - time for activity H = 16 (23-7).

At Event 5, it is LET for Event 6 - time for activity G = 9 (16-7).

At Event 4 it is Event 6 - time for activity F = 10 (16-6).

At Event 3, it is Event 6 - time for activity E = 11 (26-5).

On the diagram it would look like this:

At Event 5, the earliest time is 8 and latest time is 9. Therefore, there is float/slack of 1.

At Event 3, the earliest time is 9 and the latest time is 11. Therefor there is float/slack of 2.

Event 4 has no float/slack. EET = LET which makes it the critical event.

What would the LET for Event 2 be?

Find the LET for the critical event before Event 2. This is Event 4 and has a LET of 10.

Therefore, the LET of Event 2 is:

LET of Event 4 - time taken for Activity C = 10 - 5 = 5.

For event 1, it is always 0.

For our example above, the network diagram with EET and LET included will look like this: