Question

yy varies directly as xx. If xx = 5 then yy = 10. Find yy when xx = 13.

Answer 1

Answer:

$\begin{gathered} when\text{ x = 13:} \\ y\text{ = 26} \end{gathered}$

Explanation:

From the question, we have it that y varies directly as x

Mathematically:

$\begin{gathered} y\text{ }\propto\text{ x} \\ y\text{ = kx} \\ \end{gathered}$

where k is the constant of proportionality

When x = 5, y = 10.

Let us calculate k with this:

$\begin{gathered} 10\text{ = k }\times5 \\ k\text{ = }\frac{10}{5}\text{ = 2} \end{gathered}$

Since we have the value of k now, then:

$y\text{ = 2x}$

Now, we want to get the value of y when x = 13

Mathematically, that would be:

$\begin{gathered} y\text{ = 2 }\times\text{ 13} \\ y\text{ = 26} \end{gathered}$