CUET UG Economics Microeconomics Production Function Total Average Marginal Product Returns to Scale

Must-Know (15–20 detailed bullets)

• Production function shows the technological relationship between inputs and output: ( Q = f(L, K) ), where ( Q ) = output, ( L ) = labour, ( K ) = capital. Example: 5 workers and 2 machines produce 100 units of cloth.

• Total Product (TP) is the total output produced by a firm using given inputs over a period. If 4 labourers produce 90 units, TP = 90.

• Average Product (AP) = Total Product / Units of variable input. If TP = 80 units with 4 workers, AP = 80 ÷ 4 = 20 units per worker.

• Marginal Product (MP) is the change in TP when one more unit of variable input is added. If TP increases from 90 to 100 with an additional worker, MP = 10 units.

• MP can be calculated as ( MP_n = TP_n - TP_{n-1} ). When TP rises from 50 to 65 with the 3rd worker, MP = 15.

• AP reaches maximum when MP = AP. When MP > AP, AP rises; when MP < AP, AP falls.

• TP increases at increasing rate initially because of better division of labour and specialization.

• When MP is positive and rising, TP increases at an increasing rate. Example: MP rises from 5 to 10 → TP curve is convex.

• When MP is positive but falling, TP increases at a decreasing rate. Example: MP falls from 10 to 3 → TP curve is concave.

• TP is maximum when MP = 0. If adding the 7th worker does not increase output, MP = 0, TP peaks.

• MP can be negative; when MP < 0, TP decreases. Example: overcrowding reduces efficiency — 8th worker causes TP to fall from 100 to 95.

• Law of Diminishing Marginal Product: as more units of variable input are added to fixed input, MP eventually falls. Applies after a certain point due to fixed factor constraint.

• Returns to Scale refer to long-run changes in output when all inputs are increased proportionally.

• Increasing Returns to Scale (IRS): output increases more than proportionately. If inputs double and output becomes 2.5 times, IRS exists.

• Constant Returns to Scale (CRS): output increases exactly in proportion to input. Double inputs → double output. Example: 2L+2K → 2Q.

• Decreasing Returns to Scale (DRS): output increases less than proportionately. Double inputs → 1.5 times output.

• IRS may arise due to specialization in management and technical economies. Example: large steel plant produces per unit cheaper than small plant.

• DRS may occur due to coordination problems and managerial inefficiencies in very large firms.

• In the short run, at least one input is fixed; in the long run, all inputs are variable — crucial distinction for production function analysis.

• Verify from NCERT: exact numerical examples of TP, AP, MP schedules in Class 11 NCERT Introductory Microeconomics, Chapter 3.

Difficulty Level

Intermediate — requires understanding of conceptual differences between short-run and long-run production, and interpretation of TP, AP, MP curves.

Common CUET Traps (3 bullets)

• Trap: Confusing Diminishing Marginal Product with Decreasing Returns to Scale.
  Avoid: Diminishing MP is short-run (one input variable); Decreasing Returns to Scale is long-run (all inputs variable).

• Trap: Assuming AP falls whenever MP falls.
  Avoid: AP falls only when MP < AP; MP can fall while still being above AP, so AP continues to rise.

• Trap: Thinking TP falls when MP is positive.
  Avoid: TP falls only when MP is negative; TP rises as long as MP > 0, even if MP is falling.

Practice MCQs (5 questions)

Q1. When Marginal Product is zero, what happens to Total Product?
A. TP is increasing
B. TP is decreasing
C. TP is at its maximum
D. TP is minimum

Answer: C
Explanation: When MP = 0, TP stops increasing and reaches its peak.
Why others fail: Option A is tempting if student confuses MP > 0 with MP = 0.

Q2. Which of the following represents Constant Returns to Scale?
A. 2L + 2K → 3Q
B. 2L + 2K → 4Q
C. 2L + 2K → 2Q
D. 2L + 2K → 1.5Q

Answer: C
Explanation: Inputs doubled and output doubled → CRS.
Why others fail: Option B shows IRS (output more than doubles), which students may misidentify as CRS.

Q3. If Total Product of 5 labourers is 100 units and of 6 labourers is 110 units, what is the Marginal Product of the 6th labourer?
A. 10
B. 20
C. 110
D. 15

Answer: A
Explanation: MP = TP₆ – TP₅ = 110 – 100 = 10 units.
Why others fail: Option C (110) is TP, not MP — common confusion between total and marginal.

Q4. When Average Product is rising, Marginal Product is:
A. Equal to AP
B. Less than AP
C. Greater than AP
D. Negative

Answer: C
Explanation: AP rises when MP > AP.
Why others fail: Option A (equal) is true only at maximum AP, not during rising phase.

Q5. Which of the following is a reason for Increasing Returns to Scale?
A. Managerial inefficiency
B. Overutilization of fixed assets
C. Specialization of labour and management
D. Communication delays in large firms

Answer: C
Explanation: Specialization leads to higher efficiency, causing output to increase more than proportionately.
Why others fail: Options A and D describe DRS causes, which students may confuse with IRS.

Last‑Minute Revision (15–20 one‑liners)

• ⚠️ TP = total output; AP = TP/L; MP = ΔTP/ΔL.
• ⚠️ MP = 0 → TP is maximum.
• ⚠️ MP negative → TP falling.
• ⚠️ AP rises when MP > AP.
• ⚠️ AP falls when MP < AP.
• ⚠️ AP max when MP = AP.
• ⚠️ TP increases at increasing rate when MP is rising.
• ⚠️ TP increases at decreasing rate when MP is falling but positive.
• ⚠️ Law of Diminishing Marginal Product applies in short run.
• ⚠️ Returns to Scale apply in long run — all inputs variable.
• ⚠️ IRS: output ↑ > input ↑.
• ⚠️ CRS: output ↑ = input ↑.
• ⚠️ DRS: output ↑ < input ↑.
• ⚠️ IRS example: mass production in automobile industry.
• ⚠️ DRS example: delays in decision-making in MNCs.
• ⚠️ Short run → at least one fixed input.
• ⚠️ Long run → all inputs variable.
• ⚠️ Verify from NCERT: TP, AP, MP schedule in Class 11 Chapter 3.
• ⚠️ MP can be negative; AP cannot be negative.
• ⚠️ Production function: Q = f(L, K) — labour and capital.