Question

the ratio of incomes of two persons in 9:7 and the ratio of their expenditures is 4:3. if each of them saves rs.200 each per month. find their monthly income

Answer 1

Answer:

let the income be x and expenditure be y

for 1st person

9x - 4y = 200                      ---------------(1)

and for second

7x- 3y = 200                         ---------------(2)

now multiplying eq. 1 with 3  and eq.2 with 4 ( to eliminate one variable)

   27x - 12y = 600

--  28x - 12y = 800

------------------------------

  -x              = - 200

hence

x=200

similarly for the value of Y from eq.2

7 * 200 - 3y = 200

and hence Y =400 ( but getting the value of y isnt necessary)

now for the total income

1st person = 9x200 = 1800

2nd person = 7 x 200= 1400