The short run can be defined as the period of time during which

1. Analyze the question The question asks for the definition of the short run in economics, a concept from the theory of production and cost.

2. Explain the concept Economists classify time periods by how flexible a firm's inputs (factors of production) are:

• Short run: a period in which at least one factor of production is fixed, usually capital such as land, factory buildings or heavy machinery. The firm can still change other inputs, such as labour and raw materials, to raise or lower output.
• Long run: a period long enough for all factors of production to be varied. The firm can build a bigger factory, buy new machines or even leave the industry.
• Very long run: technology and other underlying conditions can also change.

3. Step-by-step solution

• Option A (all inputs fixed): This is wrong. If every input were fixed, the firm could not change its output at all. That situation is sometimes called the "market period" or "immediate run".
• Option B (at least one input is fixed): This is correct. It matches the standard definition. At least one input is fixed, while the others can be varied.
• Option C (at least two inputs fixed): This is wrong. The definition does not require two fixed inputs. One is enough.
• Option D (all inputs are variable): This is wrong. It describes the long run.

4. Answer B. At least one of the firm's inputs is fixed.

5. Exam tip Remember it this way: "Short run = Stuck with something." If at least one input is stuck (fixed), you are in the short run. If nothing is stuck (all variable), you are in the long run. Watch for the phrase "at least one". It is the usual wording in JAMB questions on this topic.

You are doing well. Questions like this are easy marks once you know the definitions.