Q11 of 186 Page 4

The monthly incomes of A and B are in the ratio of 5 : 4 and their monthly expenditures are in the ratio of 7 : 5. If each saves Rs. 3000 per month, find the monthly income of each.

Given ratio of incomes = 5:4

And the ratio of their expenditures = 7:5


Saving of each person = Rs. 3000


Let incomes of two persons = 5x and 4x


And their expenditures = 7y and 5y


According to the question,


5x – 7y = 3000 …(i)


4x – 5y = 3000 …(ii)


On multiplying Eq. (i) by 4 and Eq. (ii) by 5 to make the coefficients of x equal, we get


20x – 28y = 12000 …(iii)


20x – 25y = 15000 …(iv)


On subtracting Eq. (iii) from (iv), we get


20x – 25y – 20x + 28y = 15000 – 12000


3y = 3000


y = 1000


On putting the y = 1000 in Eq. (i), we get


5x – 7y = 3000


5x – 7(1000) = 3000


5x = 10000


x = 2000


Thus, monthly income of both the persons are 5(2000) and 4(2000), i.e. Rs. 10000 and Rs. 8000


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