# Example 11 - Chapter 3 Class 10 Pair of Linear Equations in Two Variables

Last updated at May 29, 2018 by Teachoo

Last updated at May 29, 2018 by Teachoo

Transcript

Example 11 The ratio of incomes of two persons is 9 : 7 and the ratio of their expenditures is 4 : 3. If each of them manages to save Rs.2000 per month, find their monthly incomes. It is given that , Ratio of income of two persons is 9:7 Let the income of 1st person be 9x & income for 2nd person be 7x. Similarly, Ratio of expenditures of two persons is 4 : 3 Let expenditure of 1st person be 4y & expenditure of 2nd person be 3y Both saves Rs 2000 per month Both saves Rs 2000 per month We know that, Income Expenditure = Savings For 1st person 9x 4y = 2000 Similarly for 2nd person 7x 3y = 2000 Now, our equations are 9x 4y = 2000 (1) 7x 3y = 2000 (2) We will solve them by elimination We know that 12 is the multiple of 3 and 4 Multiplying (1) with 3 3 ( 9x 4y) = 2000 3 27x 12y = 6000 Now we use elimination with equation (3) & (4) x = 2000 x = 2000 Putting value of x in (1) 9x 4y = 2000 9(2000) 4y = 2000 18000 4y = 2000 - 4y = 2000 18000 - 4y = - 16000 y = 16000/4 y = 4000 Hence, x = 2000, y = 4000 is the solution of the equation . Hence, Monthly income of 1st person = 9x = 9 2000 = Rs 18,000 Monthly income of 2nd person = 7x = 7 2000 = Rs 14,000

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Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.