EconomicsISC Class 11 · Basic Problems of an Economy

Production Possibility Curve, MRT and Shifts (ISC Class 11 Economics)

Updated 17 October 2026 · Fact-checked

The production possibility curve (PPC) shows the maximum combinations of two goods an economy can produce with its given resources and technology, assuming full and efficient use. Its slope is the marginal rate of transformation (MRT): the units of one good given up to gain one more unit of the other. Because MRT rises, the PPC is concave to the origin; it shifts outward with growth and rotates with a change in technology for one good.

Understand Production Possibility Curve: Opportunity Cost, MRT and Shifts

Assumptions. Two goods; fixed resources; fixed technology; full employment and efficient use of resources; resources not equally efficient in all uses.

PPC schedule (example).

Combination	Wheat (lakh tonnes)	Cloth (lakh metres)
A	0	20
B	1	18
C	2	14
D	3	8
E	4	0

MRT (marginal rate of transformation) = Loss of Y / Gain of X (the opportunity cost of one more unit of X). A to B: 2/1 = 2; B to C: 4/1 = 4; C to D: 6/1 = 6; D to E: 8/1 = 8. The MRT rises because resources are not equally suited to both goods; as more wheat is produced, resources less suited to wheat are shifted and more cloth must be given up per unit of wheat. Hence the PPC is concave to the origin.

Features. Downward sloping (a trade-off); concave (rising opportunity cost); every point on it is efficient.

Points relative to the PPC.

*On the curve:* full employment and efficient use (attainable).
*Inside the curve:* unemployment or inefficient use of resources (attainable but wasteful).
*Outside the curve:* unattainable with present resources and technology.

Shifts. *Rightward shift of the whole curve:* growth in resources or improvement in technology for both goods. *Leftward shift:* destruction of resources (war, disaster). *Rotation:* if technology improves for one good only, one intercept moves (for example, better cotton technology raises the cloth intercept, leaving wheat's intercept unchanged).

Constant opportunity cost: if resources are equally suited, the PPC is a straight line.

Production Possibility Curve: Opportunity Cost, MRT and Shifts: key facts

MRT: MRT = Loss of Y / Gain of X | Units of Y given up per unit of X gained; Slope of the PPC.
Opportunity cost of X: Cost of 1 unit of X = Y given up | Rises as more X is produced; Increasing cost.
PPC positions: Inside unemployment
On full use
Outside unattainable; Three positions.

Inside	unemployment
On	full use
Outside	unattainable

How to answer Production Possibility Curve: Opportunity Cost, MRT and Shifts questions

Use the schedule to compute MRT between neighbouring points.

1List the combinations in order.
2Find the change in each good between points.
3MRT = fall in Y / rise in X.
4Check if MRT rises, and name the shape; place any given point relative to the curve.

Production Possibility Curve: Opportunity Cost, MRT and Shifts in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Shifting resources

Suppose a village can use its labour to make 20 baskets or grow 10 kg of vegetables per day, and to get 5 kg of vegetables it must give up 4 baskets.

What is the MRT for those 5 kg, and what does a higher MRT later signal?

Try it first, then show the solutionSolution

MRT = 4 baskets / 5 kg = 0.8 baskets per kg.
If giving up more baskets is needed later for each kg, workers are less suited to vegetables, so the opportunity cost rises.

Answer: MRT = 0.8 baskets per kg; rising MRT means increasing opportunity cost.

Memory hook: Rising cost makes the PPC bow outwards.

Tricks to remember Production Possibility Curve: Opportunity Cost, MRT and Shifts

Short memory aids. Say each one aloud once, then use it on a question the same day.

In, On, Out
Inside: waste; On: efficient; Outside: impossible.
Use it when: Points.
MRT = lose over gain
MRT is Y lost per X gained.
Use it when: Calculation.
Tech for one good
One intercept moves, the curve rotates.
Use it when: Rotation.

Production Possibility Curve: Opportunity Cost, MRT and Shifts: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Position · 1 mark · MCQBoard level

A point inside the PPC indicates:
(a) full employment (b) unemployment or inefficiency (c) an unattainable level (d) growth

Try it first, then show the solutionSolution

Resources are not fully used.

Answer: (b) unemployment or inefficiency

Example 2: Features · 3 marks · Short answerBoard level

Why is the PPC concave to the origin? (3 marks)

Try it first, then show the solutionSolution

Resources are not equally efficient in all uses.
To produce more of one good, resources less suited to it are shifted.
So more of the other good is given up per unit: MRT rises.

Answer: Because the opportunity cost increases as production of one good expands, as resources are not equally suited to both goods.

Example 3: MRT table · 6 marks · Long answerHarder board level

Using the schedule (A: 0 wheat, 20 cloth; B: 1, 18; C: 2, 14; D: 3, 8; E: 4, 0), compute the MRT between successive points and the total opportunity cost of producing 3 lakh tonnes of wheat instead of none. State whether the point (2, 10) is attainable and whether (3, 12) is attainable. (6 marks)

Try it first, then show the solutionSolution

MRT: 2, 4, 6, 8; rising.
Cost of 3 lakh tonnes of wheat = 20 - 8 = 12 lakh metres of cloth.
(2, 10): for 2 lakh tonnes of wheat, the maximum cloth is 14; 10 < 14 so the point is inside: attainable but wasteful.
(3, 12): maximum cloth at 3 is 8; 12 > 8, so it is outside: unattainable.

Answer: MRT 2, 4, 6, 8; opportunity cost 12 lakh metres of cloth; (2, 10) attainable and inefficient, (3, 12) unattainable.

Example 4: Shift and rotation · 5 marks · Long answerHarder board level

In the above economy a new technique raises the maximum cloth from 20 to 25 lakh metres but wheat output cannot increase (maximum stays 4). Describe the change in the PPC and the new opportunity cost of 4 lakh tonnes of wheat. If instead both maxima rose by 20%, find the new maxima. (5 marks)

Try it first, then show the solutionSolution

Only the cloth intercept moves: the PPC rotates (pivots at the wheat intercept).
Opportunity cost of 4 lakh tonnes of wheat = all 25 lakh metres of cloth.
Both rise 20%: wheat 4 x 1.2 = 4.8 lakh tonnes; cloth 20 x 1.2 = 24 lakh metres; the PPC shifts outward.

Answer: The PPC rotates; the cost of 4 lakh tonnes of wheat becomes 25 lakh metres of cloth. A 20% rise in both maxima gives 4.8 and 24, a parallel-like outward shift.

Example 5: Evaluate a policy · 5 marks · Long answerHOTS / competency

A country on its PPC chooses combination D (3 wheat, 8 cloth) in a year with wheat shortages and moves to E (4 wheat, 0 cloth). Find the extra wheat and the cloth given up, discuss the opportunity cost and say whether an economy inside the curve could gain both goods. (5 marks)

Try it first, then show the solutionSolution

Extra wheat = 1 lakh tonnes; cloth given up = 8 lakh metres.
The MRT is 8: very high, because the last wheat comes from resources best suited to cloth.
An economy inside the curve has unemployed or misused resources, so it can raise both goods at once by employing them.
So moves on the curve involve a trade-off, but moves from inside to the curve do not.

Answer: 1 lakh tonnes of wheat costs 8 lakh metres of cloth; an economy inside the curve can gain both goods by using idle resources.

Where students lose marks in Production Possibility Curve: Opportunity Cost, MRT and Shifts

The slips examiners see most often, and what to write instead.

Mistake: Computing MRT as gain of Y over loss of X
Inverted ratio.
Wrong working
1/2
Right working
2/1 = 2
Do this: Lose Y over gain X.
Usually costs: 2 marks.
Mistake: Calling a point outside the PPC attainable
Confusing with growth.
Wrong working
(3, 12) is attainable
Right working
(3, 12) is unattainable
Do this: Compare with the maximum.
Usually costs: 1-2 marks.
Mistake: Drawing a rotation as a parallel shift
Neglecting one good.
Wrong working
Both intercepts move
Right working
Only one intercept moves
Do this: Technology for one good rotates.
Usually costs: 1 mark.

Exam tips

Always show the MRT table.
Use the words "attainable" and "efficient" correctly.
Draw and label the intercepts when describing shifts.

Practice questions on Production Possibility Curve: Opportunity Cost, MRT and Shifts

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
The slope of the PPC is called:
(a) marginal utility (b) marginal rate of transformation (c) elasticity (d) average cost
Hint
Trade-off ratio.
Answer
(b) marginal rate of transformation
Q2 · 3 marks · Short answerBoard level
State any three assumptions of the PPC. (3 marks)
Hint
Resources, technology, employment.
Answer
Two goods, given resources and technology, full employment and efficient use of resources.
Q3 · 5 marks · Long answerHarder board level
A PPC schedule: P (0 tractors, 15 tonnes of grain); Q (1, 14); R (2, 12); S (3, 9); T (4, 5); U (5, 0). Find the MRT between successive points, say whether the PPC is concave, and whether the combinations (3, 11) and (2, 10) are attainable and efficient. (5 marks)
Hint
Differences in grain: 1, 2, 3, 4, 5.
Answer
MRT: 1, 2, 3, 4, 5, rising, so the PPC is concave. For 3 tractors the maximum grain is 9: (3, 11) is outside and unattainable. For 2 tractors the maximum is 12: (2, 10) is inside, attainable but inefficient.
Q4 · 4 marks · Short answerHarder board level
An economy is on its PPC producing 6 units of X and 30 units of Y. To raise X to 9 units it must give up 8 units of Y; to raise X from 9 to 12 units it must give up 12 more units of Y. Find the MRT for each step and the combination at X = 12, and say whether the opportunity cost is rising. (4 marks)
Hint
Divide Y lost by X gained.
Answer
Step 1: MRT = 8/3 = 2.67; Y = 22. Step 2: MRT = 12/3 = 4; Y = 10. The combination at X = 12 is (12, 10). The MRT rises, so the opportunity cost is increasing.
Q5 · 4 marks · Short answerHOTS / competency
A war destroys a large part of a country's factories and farms. Explain what happens to its PPC, the output it can reach and what policy might restore it. (4 marks)
Hint
Leftward shift.
Answer
The PPC shifts left because resources and capital are destroyed. The economy can produce less of both goods. Rebuilding capital, training workers and importing technology can shift the curve outward again.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.MRT formula?Show answer
Loss of Y / Gain of X.
2.Why concave?Show answer
Rising opportunity cost.
3.Point inside means?Show answer
Unemployment or inefficiency.
4.Technology for one good causes?Show answer
Rotation of the PPC.
5.Growth causes?Show answer
Outward shift.

Production Possibility Curve: Opportunity Cost, MRT and Shifts: frequently asked questions

Can the PPC be a straight line?

Yes, with constant opportunity cost.

Is a point on the PPC always desirable?

It is efficient, but the choice depends on needs.

What does an outward shift show?

Economic growth.

Is MRT constant?

Not on a concave PPC.