Question

Given that x and y are in direct proportion, and $y_1,y_2$ are values of $y$ corresponding to the values $x_1,x_2$ of $x$ respectively. Which of the following is correct?

• A. x₁y₂=x₂y₁
• B. x₁y₁=x₂y₂
• C. x₁x₂=y₁y₂
• D. =

Answer 1

The correct option is A

x₁y₂=x₂y₁

When $x$ and $y$ are in direct proportion, we can write

$\frac{x_1}{y_1}=\frac{x_2}{y_2}$

[$y_1,y_2$ are values of $y$ corresponding to the values $x_1,x_2$ of $x$ respectively]

which gives

$x_1{y}_2=x_2{y}_1$.