QUESTION

CSAT

Easy

Maths

Prelims 2017

The monthly incomes of X and Y are in the ratio of 4:34 : 3, and their monthly expenses are in the ratio of 3:23 : 2. However, each saves Rs. 6,000 per month. What is their total monthly income?

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Explanation

Step 1: Let the monthly incomes of X and Y be 4a4a and 3a3a, respectively. Step 2: Let the monthly expenses of X and Y be 3b3b and 2b2b, respectively. Step 3: Savings of X = Income of X - Expenses of X = 4a3b=6,0004a - 3b = 6,000 Step 4: Savings of Y = Income of Y - Expenses of Y = 3a2b=6,0003a - 2b = 6,000 Step 5: Solve the system of equations:

  • 4a3b=6,0004a - 3b = 6,000 → Equation 1
  • 3a2b=6,0003a - 2b = 6,000 → Equation 2 Step 6: Multiply Equation 2 by 3: 9a6b=18,0009a - 6b = 18,000 Step 7: Multiply Equation 1 by 2: 8a6b=12,0008a - 6b = 12,000 Step 8: Subtract the second equation from the first:
  • (9a6b)(8a6b)=18,00012,000(9a - 6b) - (8a - 6b) = 18,000 - 12,000
  • a=6,000a = 6,000 Step 9: Substitute a=6,000a = 6,000 into Equation 1:
  • 4(6,000)3b=6,0004(6,000) - 3b = 6,000
  • 24,0003b=6,00024,000 - 3b = 6,000
  • 3b=18,0003b = 18,000
  • b=6,000b = 6,000 Step 10: Total income = 4a+3a=7a=7×6,000=42,0004a + 3a = 7a = 7 \times 6,000 = 42,000 Final Answer: Total monthly income = Rs. 42,000

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