SOLUTION

Dummy activity (zero time activity)

• An activity that takes no time or resources whatsoever is called dummy activity or zero time activity.
• It is an assumed activity that is represented by the dashed arrow.
• A dummy is an artificial activity introduced in a network to maintain a unique numbering system for the different activities.
• It Keeps the logical sequence of activities and their interrelationships correct.
• In most projects, many activities can be performed concurrently or simultaneously.
• It is possible that two activities could be drawn by the same beginning and end events.
• In situations where two or more activities can be performed concurrently, the concept of dummy activity is introduced to resolve this problem.
• The concept of dummy enables all activities in a project to be shown by only one arrow for each.
• In other words, a dummy is some job or task which stipulates a necessary time orientation but the activity takes no time or resources in itself.
• These are used to represent a situation where one event cannot take place until a previous event has been completed,