Question

If $x+y=25$ and $\frac{100}{x+y}+\frac{30}{x-y}=6$, then the value of $x-y$ is

• A. $18$
• B. $20$
• C. $15$
• D. $10$

Answer 1

Answer: (C)

$15$

$x+y=25$ .................. (1)

$\frac{100}{x+y}+\frac{30}{x-y}=6$ ................... (2)

Substitute $x+y=25$ in equation (2),

$\frac{100}{25}+\frac{30}{x-y}=6$

$4+\frac{30}{x-y}=6$

$\frac{30}{x-y}=6-4=2$

$30=2\times (x-y)$

$\Rightarrow x-y=\frac{30}{2}=15$