Question

If $(x+y):(x-y)$ is equal to the duplicate ratio of $3:1$, then $x:y=$ _____

• A. $1:3$
• B. $4:5$
• C. $5:4$
• D. $3:1$

Answer 1

The correct option is C $5:4$

The duplicate ratio of $a:b$ is $a^2:b^2$
$\therefore$ The duplicate ratio of $3:1$ is $9:1$.
$\therefore \frac{x+y}{x-y}=\frac{9}{1}$
$\therefore x+y=9x-9y$
$\therefore y+9y=9x-x$
$\therefore 10y=8x$
$\therefore \frac{x}{y}=\frac{10}{8}=\frac{5}{4}$
$\therefore x:y=5:4$.