2.14

## The Open University

Skip to 0 minutes and 4 secondsSPEAKER: In this video, we will show you how to use a Gantt chart to work out the possible effects of delays on a project with parallel activities. We will demonstrate this by sharing a simple project, preparing lunch.

Skip to 0 minutes and 18 secondsThis project is just four activities: shopping, cooking, laying the table, and eating, and is scheduled to last two hours, or 120 minutes. Of the four activities, activity A, shopping, and D, eating, are sequential. While Activity B, cooking, and C, laying the table, are parallel. This means that while the cooking and clearing can start once the shopping has been done, Tom and Sarah will have to wait until both of these activities are complete before they can eat. So Tom will have to wait 20 minutes after laying the table before eating with Sarah. But what would happen if Tom decided to wait a bit before laying the table?

Skip to 1 minute and 3 secondsAs you can see from the Gantt chart, Tom doesn't have to start laying the table immediately. He has the time to delay this without affecting the project duration. In other words, activity C can float without making the project last any longer. Therefore, Tom decides to play on his games console for 20 minutes before starting to lay the table. However, if Sarah decides to delay the cooking by 10 minutes, the situation is quite different. As you can see, the overall duration of the project is affected, it is now 10 minutes late. So you can see that there are different effects of delays on the duration of the project, depending on which of the parallel activities is delayed.

Skip to 1 minute and 47 secondsSo these activities, A, B, and D, are said to be on a critical path. The critical activities are the activities that cannot be delayed without affecting the duration of a project.

# Parallel activities and project duration

At the beginning of the week, you examined how Gantt charts can be used to plot out different project activities, now you’re going to look in more detail at how delays to the activities can impact the delivery of your project. The project here is Sarah and her teenage son Tom preparing lunch.

There are some projects that need to be completed by a certain date, for instance, the preparations for the Olympic Games or your study for an exam: they need to be done in time for the due date. Nevertheless, delays in projects are very common, so it is wise to be clear about which activities can be delayed without affecting the overall duration of a project and which activities are critical to the project ending on time.

This video illustrates how delays can affect a project with parallel activities in different ways. Project activities may have differing durations or dependencies, which indicates that it might be possible for one of these activities to ‘float’ (the activity can be delayed without causing changes to the overall duration of the project).