Question

Which of the following equations represents a direct proportional relationship between $x$ and $y$?

• A. $4y=x^3$
• B. $y=2x^4$
• C. $5y=4x^2$
• D. $y=4x$

Answer 1

The correct option is D $y=4x$

Let’s take an example.
If the total cost $y$ is proportional to the number of items $x$ purchased at a constant price $4$, the direct proportional relationship between the total cost and the number of items can be expressed as $y=4x$.