Calculate float times

A question is this type if and only if it asks you to calculate total float, independent float, or interfering float for specific activities.

2 questions · Moderate -0.8

7.05a Critical path analysis: activity on arc networks7.05b Forward and backward pass: earliest/latest times, critical activities
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OCR MEI D1 2005 June Q3
8 marks Moderate -0.8
3 Table 3 gives the durations and immediate predecessors for the five activities of a project. \begin{table}[h]
ActivityDuration (hours)Immediate predecessor(s)
A3-
B2-
C5-
D2A
E1A, B
\captionsetup{labelformat=empty} \caption{Table 3}
\end{table}
  1. Draw an activity-on-arc network to represent the precedences.
  2. Find the early and late event times for the vertices of your network, and list the critical activities.
  3. Give the total and independent float for each activity which is not critical.
OCR MEI D1 2007 January Q4
16 marks Moderate -0.8
Cassi is managing the building of a house. The table shows the major activities that are involved, their durations and their precedences.
ActivityDuration (days)Immediate predecessors
ABuild concrete frame10\(-\)
BLay bricks7A
CLay roof tiles10A
DFirst fit electrics5B
EFirst fit plumbing4B
FPlastering6C, D, E
GSecond fit electrics3F
HSecond fit plumbing2F
ITiling10G, H
JFit sanitary ware2H
KFit windows and doors5I
  1. Draw an activity-on-arc network to represent this information. [5]
  2. Find the early time and the late time for each event. Give the project duration and list the critical activities. [6]
  3. Calculate total and independent floats for each non-critical activity. [2]
Cassi's clients wish to take delivery in 42 days. Some durations can be reduced, at extra cost, to achieve this.
  • The tiler will finish activity I in 9 days for an extra £250, or in 8 days for an extra £500.
  • The bricklayer will cut his total of 7 days on activity B by up to 3 days at an extra cost of £350 per day.
  • The electrician could be paid £300 more to cut a day off activity D, or £600 more to cut two days.
  1. What is the cheapest way in which Cassi can get the house built in 42 days? [3]