The monthly incomes of two friends Chetan and Vipul, are in the ratio 5 : 7 respectively and each of them saves ₹72000 every month. If the ratio of their monthly expenditure is 1 : 3, find the monthly income of Chetan(in ₹).

Given:

Ratio of monthly incomes of Chetan and Vipul = 5 : 7

Each saves ₹72000 every month.

Ratio of their monthly expenditure = 1 : 3

Formula Used:

Income - Savings = Expenditure

Calculation:

Let the monthly income of Chetan be 5x and the monthly income of Vipul be 7x.

Each saves ₹72000, so:

Chetan's expenditure = 5x - 72000

Vipul's expenditure = 7x - 72000

The ratio of their monthly expenditure is 1 : 3, so:

\(\frac{\text{Chetan's expenditure}}{\text{Vipul's expenditure}} = \frac{1}{3}\)

⇒ \(\frac{5x - 72000}{7x - 72000} = \frac{1}{3}\)

⇒ 3 × (5x - 72000) = 1 × (7x - 72000)

⇒ 15x - 216000 = 7x - 72000

⇒ 15x - 7x = 216000 - 72000

⇒ 8x = 144000

⇒ \(x = \frac{144000}{8}\)

⇒ x = 18000

Chetan's monthly income = 5x = 5 × 18000 = ₹90000

∴ The monthly income of Chetan is ₹90000.