If $2 x+y=5$ and $3 x-4 y=2$, then the value of $2 x y$ is
(a)4
(b)6
(c)8
(d)10
Answer
Answer (as printed): A
Explanation
$2 x+y=5 \quad \ldots(i)$ and $3 x-4 y=2 \quad \ldots(i i)$ Multiplying (i) by 4 and adding (ii) to it, we get: $11 x=22$ or $x=2$. Putting $x=2$ in (i), we get: $y=1$. So, $2 x y=2 \times 2 \times 1=4$.
Explanation as extracted from the printed page; notation may be imperfect.