Time Management and Scheduling: Network Diagrams, CPM, PERT and Gantt Charts Questions

Question 1

Write PERT expected time formula.

Accepted Answer

**te = (to + 4tm + tp) / 6**.

Question 2

What is a Gantt chart?

Accepted Answer

A **Gantt chart** is a bar chart showing activities versus time.

Question 3

Define PERT.

Accepted Answer

**PERT** is a scheduling technique using probabilistic time estimates for uncertain activities.

Question 4

Define CPM.

Accepted Answer

**CPM** (Critical Path Method) is a scheduling technique to identify the **critical path** using known activity durations.

Question 5

Define critical path.

Accepted Answer

**Critical path** is the longest-duration path in the network and determines minimum project duration.

Question 6

What is float?

Accepted Answer

**Float (slack)** is the allowable delay for an activity without delaying project completion.

Question 7

Explain forward pass and backward pass in CPM.

Accepted Answer

In **forward pass**, we calculate **ES** and **EF** using `EF = ES + duration`. In **backward pass**, we calculate **LF** and **LS** using `LS = LF − duration`. These help find float and critical path.

Question 8

Explain critical path and its importance.

Accepted Answer

Critical path is the **longest** path in the network. Activities on it have **zero float**. Importance: it gives minimum project duration and any delay in critical activities delays the whole project.

Question 9

Explain total float and give formula.

Accepted Answer

Total float is the time an activity can be delayed without affecting project end date. Formula: **TF = LS − ES = LF − EF**. If TF=0, activity is critical.

Question 10

Explain PERT time estimates and expected time.

Accepted Answer

PERT uses **to** (optimistic), **tm** (most likely), **tp** (pessimistic). Expected time is **te = (to + 4tm + tp)/6** which gives higher weight to most likely time.

Question 11

Differentiate CPM and PERT (any three points).

Accepted Answer

CPM uses deterministic durations; PERT uses probabilistic estimates. CPM suits routine projects; PERT suits uncertain/R&D. CPM focuses on critical path control; PERT focuses on uncertainty handling.

Question 12

Explain Gantt chart with one benefit and one limitation.

Accepted Answer

A **Gantt chart** shows activities as bars on a timeline. Benefit: easy to understand and track progress. Limitation: in large projects, dependencies and complexity are hard to show clearly.

Question 13

Explain CPM and critical path method with steps and table/flow.

Accepted Answer

### **Explain CPM and critical path with steps (flow + table)**

**CPM (Critical Path Method)** is a scheduling technique used when activity durations are known.

**Steps**:
1) list activities, durations, dependencies
2) draw network diagram
3) forward pass to find **ES/EF**
4) backward pass to find **LS/LF**
5) compute **float** and identify **critical path**

| Term | Meaning |
|---|---|
| ES/EF | earliest start/finish |
| LS/LF | latest start/finish |
| Float | allowable delay |
| Critical path | longest path, zero float |

```text
Forward pass → Backward pass → Float → Critical path
```

Thus CPM identifies minimum project duration and activities that must not be delayed.

Question 14

Explain PERT and expected time calculation with formula and table.

Accepted Answer

### **Explain PERT and expected time calculation with formula**

**PERT** is used when activity durations are uncertain.

It uses three estimates:
- **to** optimistic
- **tm** most likely
- **tp** pessimistic

Expected time:
- **te = (to + 4tm + tp) / 6**

| Estimate | Meaning |
|---|---|
| to | optimistic time |
| tm | most likely time |
| tp | pessimistic time |
| te | expected time |

```text
Uncertain durations → take 3 estimates → compute expected time → schedule
```

Hence PERT provides a more realistic schedule under uncertainty.

Question 15

Differentiate CPM and PERT and explain how Gantt chart is used in scheduling.

Accepted Answer

### **Differentiate CPM and PERT and mention Gantt chart use**

| Basis | **CPM** | **PERT** |
|---|---|---|
| Time estimates | deterministic | probabilistic |
| Best for | routine projects | R&D/uncertain projects |
| Focus | critical path & control | uncertainty handling |

**Gantt chart** is a bar chart showing activities against time; it is easy to understand and helps communicate schedule progress.

```text
Network methods (CPM/PERT) → compute schedule → present on Gantt chart
```

Thus CPM/PERT compute schedule logic, and Gantt helps visualize and track it.

Time Management and Scheduling: Network Diagrams, CPM, PERT and Gantt Charts

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