Are activity bars labelled with their float?

No. Bars are labelled with **activity name and duration**. The float (dotted part) is **not** labelled.

What is the other name for a Gantt chart?

A Gantt chart is also called a **cascade chart**.

What assumption does a Gantt chart make about workers?

A Gantt chart assumes **one worker per activity** (or one resource/team per activity).

How are critical activities drawn on a Gantt chart?

Critical activities are drawn **back-to-back** on the **same horizontal line**. They have zero float, so they form one continuous bar from start to finish of the project.

How are non-critical activities drawn on a Gantt chart?

Each non-critical activity is on a **separate line**. A **solid bar** shows the activity at its earliest start (length = duration). A **dotted bar** shows the **total float** — the flexibility to delay.

What does the dotted part of a non-critical activity bar represent?

The **dotted bar** represents the **total float** — the time the activity can be delayed without affecting the minimum project duration. It is the 'room' the solid bar can slide within.

At what time does each activity start on a Gantt chart?

Each activity is assumed to start at its **earliest event time** (the early event time at its start node). The chart shows the earliest possible schedule.

Can an activity have breaks in the middle on a Gantt chart?

No. Each activity is assumed to occur in a **single block of time** with no breaks. Once started, it runs continuously for its duration.

How long should the time axis extend?

The axis should extend from 0 to at least the **minimum project duration**. For a 23-day project, 0 to 25 is often used for clarity.

Gantt (Cascade) Charts | Pearson Edexcel International AS Maths

Q: What is a Gantt chart?

A **Gantt chart** (cascade chart) is a graphical display of project activities as **horizontal bars** against a **time axis**. It shows critical activities, total float for non-critical activities, and the minimum project duration.

Critical Path Analysis

Gantt (Cascade) Charts

Summary

A Gantt chart (or cascade chart) is a graphical display of project activities as horizontal bars against a time axis. It shows critical activities (drawn back-to-back on one line), non-critical activities (each on a separate line with dotted float bars), and the minimum project duration. Gantt charts are used in scheduling to visualise when activities occur and how much flexibility non-critical activities have.

1. What is a Gantt Chart?

A Gantt chart (cascade chart) is a graphical display of the activities in a project. It shows: critical activities, total float for non-critical activities, and the minimum project duration.

Gantt charts are used in scheduling problems. The chart assumes one worker per activity.

A horizontal time axis is drawn; activities are shown as bars (rectangles) below it.

Each activity is assumed to start at its earliest event time and run in a single block with no breaks.

2. Drawing Critical Activities

Critical activities have total float zero. They are drawn back-to-back on the same horizontal line.

They form a continuous sequence from the start of the project to the end, with no gaps.

Example: If the critical path is A-C-G-I, these four activities appear as one continuous bar on the top row.

3. Drawing Non-Critical Activities

Each non-critical activity is drawn on a separate line.

A solid bar shows the activity at its earliest start time, with length = duration.

A dotted bar extends to show the total float — the 'room' the activity can slide within. The dotted part represents the flexibility.

Example: Activity of duration 4, early start 7, total float 3: solid bar 7–11, dotted bar 11–14. Bars are labelled with activity name and duration; floats are not labelled.

4. Construction Steps

Draw a horizontal axis from 0 to at least the minimum project duration (e.g. 0 to 25 for a 23-day project).

Place critical activities back-to-back on the first row.

Place each non-critical activity on its own row: solid bar from earliest start for duration, then dotted bar for float.

Label bars with activity name and duration. Do not label the float (dotted) sections.

5. Example

6. Examiner Tips