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NSWMaths Standard 2Quick questions

Year 12: Networks

Quick questions on Forward and backward scanning and activity float for HSC Maths Standard 2

11short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is forward scanning (earliest times)?
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Label each event (node) with the earliest time it can occur, computed by working forward from the project start.
What is backward scanning (latest times)?
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Label each event with the latest time it can occur without delaying the project, computed by working backward from the project end.
What is time computations for each activity?
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For activity from event ii to event jj with duration tt:
What is float?
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The float of an activity is the maximum delay possible without extending the project:
What is critical path?
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The critical path consists of activities with zero float. It is also the longest path through the network (the same path found in the previous dot point's analysis).
What is compact notation?
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The HSC often uses a four-quadrant notation per event:
What is australian construction (extension to previous example)?
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Forward: Event 11 EST 00; Event 22 (after AA) EST 44; Event 33 (after BB) EST 1010; Event 44 (after CC and DD) EST max(10+3,10+4)=14\max(10 + 3, 10 + 4) = 14; Event 55 (after EE) EST 1919; Event 66 (after FF) EST 2626.
What is confusing event times with activity times?
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EST and LFT are properties of events (nodes). Each activity's EST is the EST of its start event; each activity's LFT is the LFT of its end event.
What is off-by-one on float?
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Float == LFT - EST - duration. Easy to forget the duration.
What is calling the shortest path critical?
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The critical path is the LONGEST, made up of zero-float activities.
What is forgetting to label all events?
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Every event needs both EST and LFT. Use a clear two-number labelling. :::

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