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Edexcel IAL - Decision Mathematics 1- 4.2 Completion of Precedence Tables- Study notes  - New syllabus

Edexcel IAL – Decision Mathematics 1- 4.2 Completion of Precedence Tables -Study notes- New syllabus

Edexcel IAL – Decision Mathematics 1- 4.2 Completion of Precedence Tables -Study notes -Edexcel A level Maths- per latest Syllabus.

Key Concepts:

  • 4.2 Completion of Precedence Tables

Edexcel IAL Maths-Study Notes- All Topics

Completion of a Precedence Table from an Activity Network

A precedence table shows each activity in a project together with its immediate predecessor(s). In this syllabus, students may be required to complete a precedence table when an activity-on-arc (AOA) network is given.

Key Idea

The immediate predecessors of an activity are the activities that must be completed directly before it can start.

Only immediate predecessors are listed. Activities that occur earlier but are connected indirectly are not included.

Method for Completing a Precedence Table

To complete a precedence table from an activity network:

  1. Identify each activity (arrow) in the network
  2. For a given activity, find the node where it starts
  3. All activities that end at this node are its immediate predecessors
  4. If an activity starts at the initial node, it has no predecessors

Dummy Activities

Dummy activities:

  • Have zero duration
  • Are included only to preserve precedence relationships

Dummy activities are not listed as activities in the precedence table, but they may affect which activities are predecessors.

Important Points

  • Each activity appears once in the table
  • Predecessors must be activities, not event numbers
  • Only direct dependencies are listed

Example :

Draw the network from the predecessor table.

ActivityImmediate predecessor
A–
BA
CA
DA
EB
FC
GD
HE, F, G
Construct the activity network diagram using the given predecessors.
▶️ Answer/Explanation

Example :

Explain why an activity connected only through a dummy may still be an immediate predecessor.

▶️ Answer/Explanation

The dummy represents a dependency without duration.

If an activity must finish before another can start, it is an immediate predecessor even if the link includes a dummy.

Conclusion: Dummy activities preserve correct precedence relationships.

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