Learn all Concepts of Chapter 3 Class 10 (with VIDEOS). Check - Linear Equations in 2 Variables - Class 10     1. Chapter 3 Class 10 Pair of Linear Equations in Two Variables
2. Serial order wise
3. Examples

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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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