(C) 10
41. If (3x – y) = (x + 5y) = 5:7, then the
value of (x + y) : (x – y) is:​

1 thought on “(C) 10<br />41. If (3x – y) = (x + 5y) = 5:7, then the<br />value of (x + y) : (x – y) is:​”

1. In ratios, the numerator of LHS is equal to numerator of RHS and same with the denominators.

   Here,

   • 3x – y = 5 —-(i) × 1
   • x + 5y = 7 —-(ii) × 3

   Equation (i) becomes, 3x – y = 5 —-(a)

   Equation (ii) becomes, 3x + 15y = 21 —(b)

   Subtracting equation (a) from equation (b), we get,

   → 3x + 15y – (3x – y) = 21 – 5

   → 3x + 15y – 3x + y = 16

   → 16y = 16

   → y = 1

   From equation (ii), we have

   x = 7 – 5y

   x = 7 – 5(1)

   x = 7 – 5 = 2

   Thus,

   [tex] \mapsto \: \tt \frac{x + y}{x – y} \\ \\ \mapsto \: \sf \frac{2 + 1}{2 – 1} = \frac{3}{1} \\ [/tex]

   Hence,

   • (x + y) : (x – y) = 3 : 1

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