This is the basic and conceptual question from linear equations in two variables in which we have to find the monthly income of a and b if their monthly expenditures ratio is given and it is also given that each saves 9000 per month.
Kindly give me a detailed solution of this question
RS Aggarwal, Class 10, chapter 3E, question no 29
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