Question

The values of x and y vary directlyand one pair of values are given.Write an equation that relates xand y.x = 2, y = 5·?y =X

Answer 1

We need to write an equation that relates x and y.

We know those values vary directly. And one pair of values are given. Thus, we have the following proportion:

values of x values of y

2 5

x y

Then, cross multiplying the above quantities, we obtain:

$2\cdot y=5\cdot x$

Now, we need to isolate y on the left side of the equation. We can do so by dividing both sides of the equation by 2. We obtain:

$\begin{gathered} \frac{2}{2}\cdot y=\frac{5}{2}\cdot x \\ \\ 1\cdot y=\frac{5}{2}x \\ \\ y=\frac{5}{2}x \end{gathered}$

Answer

$y=\frac{5}{2}x$