Under the utility approach, a consumer attains equilibrium in case of two commodities when the consumer spends his income in such a way that the ratio of the marginal utility of a commodity to its price is equal to the ratio of the marginal utility of the other commodity to its price. Mathematically, the condition is expressed as:
(i)\({MU_X\over P_X}={MU_Y\over P_Y}\)
(ii)MU should decrease with increase in consumption.
Example: Suppose a consumer's income is Rs.30 which he wants to spend on two goods X and Y. The price of each unit of X and Y is Rs.4 and Rs.2. Marginal utility schedule of X and Y is given as

		Where P_X=Rs.4given	where P_Y=Rs.2 given
Units	MU_X	MU_X/P_X	MU_Y	MU_Y/P_Y
1	80	80/4=20	40	40/2=20
2	72	72/4=18	38	38/2=19
3	64	64/4=16	36	36/2=18
4	56	56/4=14	34	34/2=17
5	48	48/4=12	32	32/2=16
6	40	40/4=10	30	30/2=15
7	32	32/4=8	28	28/2=14
8	24	24/4=6	26	26/2=13
9	16	16/4=4	24	24=/2=12
10	8	8/4=2	22	22/2=11

Note: (Schedule given is for understanding purpose only.)
It is evident from the table that in order to have maximum utility, consumer will purchase 4 units of X and 7 units of Y because this combination of goods satisfies the following two conditions:
At 4 units of \(X={MU_X\over P_X}={56\over4}=14\)
At 7 units of \(Y={MU_Y\over P_Y}={28\over 2}=14\)
\({MU_X\over P_X}={MU_Y\over P_Y}\)
Further, Expenditure on X + Expenditure on Y = TotalIncome
P_x . Q_x + P_y.Q_y = M
4 X 4 + 2 X 7 = ~ 30