ICSE Class 10 Economics: Consumer’s Equilibrium Made Simple

Why Care About Consumer’s Equilibrium?

Ever wondered why you buy a snack and a soda in just the right amounts? That's consumer’s equilibrium at work – the sweet spot where your money brings you the most happiness.

💡 In Simple Words: Consumer’s equilibrium is the point where a shopper spends their budget so that the extra happiness (called marginal utility) they get from the last rupee spent on any product is the same for all products. In other words, you can't feel better by shifting money from one item to another.

What Exactly Is Consumer’s Equilibrium?

Consumer’s equilibrium means a buyer has arranged their purchases so that the marginal utility per rupee (extra happiness per unit of money) is equal for every good they buy. Marginal utility is just the extra satisfaction you get from one more unit of something – think of it like the extra splash you feel when you turn the faucet on a little more.

Key Terms Explained

• Marginal Utility (MU): the extra happiness from one additional unit of a product.
• Marginal Utility per Rupee (MU/R): MU divided by the price of that unit – it tells you how much happiness you get for each rupee spent.
• Budget Constraint: the line that shows all the combinations of goods you can afford with your income.

How to Find the Equilibrium – A Simple Flow

Worked Example

Riya has ₹100 to spend on two items: chocolates (price ₹10 each) and juice (price ₹20 each). Her marginal utilities are:

• 1st chocolate = 30 utils, 2nd = 20 utils, 3rd = 10 utils.
• 1st juice = 40 utils, 2nd = 15 utils.

Step 1: Compute MU/R.

• Chocolate MU/R = 30/10 = 3, then 20/10 = 2, then 10/10 = 1.
• Juice MU/R = 40/20 = 2, then 15/20 = 0.75.

Step 2: Spend where MU/R is highest. First buy a chocolate (MU/R=3). Money left: ₹90. Step 3: Re‑calculate – next highest MU/R is juice (2). Buy one juice. Money left: ₹70. Step 4: Continue: second chocolate (MU/R=2) – buy it. Money left: ₹60. Step 5: Now both chocolate (next MU/R=1) and juice (next MU/R=0.75) are lower, but chocolate still gives more per rupee, so buy another chocolate. Money left: ₹50. Step 6: Keep buying until the next MU/R for chocolate drops to 0.75 or lower. After buying the fifth chocolate, MU/R becomes 0.5, lower than juice’s 0.75, so stop buying chocolates and buy another juice.

When Riya finishes, the MU/R of the last chocolate (0.5) equals the MU/R of the last juice (0.75) as closely as her budget allows – that’s her equilibrium.

Quick Comparison Table

Condition	What It Means
MU/R equal for all goods	Consumer is at equilibrium – no better re‑allocation possible.
MU/R higher for one good	Buy more of that good and less of the other until equality.
Budget fully spent	All money used; otherwise you could increase total utility by spending the leftover.

Bullet‑Point Summary

• Equilibrium occurs when MU per rupee is the same for every product.
• Always spend the whole budget – any unspent money is a missed chance for extra happiness.
• Adjust purchases step by step: buy the good with the highest MU/R, then recalc.
• Think of MU/R like the “bang for your buck” ratio.

📝 Likely Exam Questions

1. Define consumer’s equilibrium.
   Answer: It is the situation where a consumer allocates his/her income such that the marginal utility per rupee spent on each commodity is equal, and the entire budget is exhausted.
2. Explain why a consumer will keep shifting expenditure from one good to another until MU/R are equal.
   Answer: If MU/R of one good is higher, moving a rupee from the lower‑MU/R good to the higher‑MU/R good increases total utility, so the consumer will continue until no further gain is possible, i.e., MU/R equal.
3. Rohan has ₹150 to spend on books (₹30 each) and pens (₹10 each). The marginal utilities are: first book 90, second 60, third 30; first pen 40, second 30, third 20, fourth 10. Find his equilibrium bundle.
   Answer: Compute MU/R – Book: 90/30=3, 60/30=2, 30/30=1. Pen: 40/10=4, 30/10=3, 20/10=2, 10/10=1. Start with highest MU/R (pen 4) – buy one pen (₹10). Remaining ₹140. Next highest MU/R is book 3 and pen 3 – choose either; buy one book (₹30). Remaining ₹110. Continue buying items with MU/R = 3 (second pen, second book) until budget runs out. Final bundle: 2 books (₹60) + 9 pens (₹90) = ₹150, where the last pen’s MU/R = 1 equals the next book’s MU/R = 1, indicating equilibrium.
4. What would happen if a consumer’s MU/R for one good is higher than for another, but the consumer does not change his spending?
   Answer: Total utility would be lower than possible; the consumer could increase satisfaction by reallocating money to the higher MU/R good.
5. State two assumptions underlying the concept of consumer’s equilibrium.
   Answer: (i) The consumer aims to maximize total utility. (ii) Prices of goods remain constant while the consumer decides how to spend the income.