Assume there are four families in a country. The average per capita income of these families is Rs 5000. If the income of three families is Rs 4000, Rs 7000 and Rs 3000 respectively, what is the income of the fourth family?

1. Rs 7500
2. Rs 3000
3. Rs 2000
4. Rs 6000

Rs 6000

Solution: Per capita income is the total income of the country/state divided by the number of people in that country/state.

There are total four families.

Let the income of fourth family be x

The average per capita income is

(4000 + 7000 + 3000 + x) / 4 = 5000

⇒ (14000 + x) / 4 = 5000

⇒ 14000 + x = 5000 x 4

⇒ 14000 + x = 20000

⇒ x = 20000 - 14000

⇒ x = 6000

∴ Income of fourth family is Rs. 6,000.