Question

y is in direct proportion to x. If x = 25 than y = 5. Find the value of y, if x = 9.

Answer 1

Given

y is in direct proportion to x.

And, if x = 25 then y = 5.

To find the value of y if x=9.

Explanation:

It is given that,

y is in direct proportion to x.

Then,

$\begin{gathered} y\propto x \\ y=kx\text{ \_\_\_\_\_\lparen1\rparen} \end{gathered}$

Since, x=25 and y=5.

Then,

$\begin{gathered} 5=k(25) \\ k=\frac{5}{25} \\ k=\frac{1}{5} \end{gathered}$

Therefore,

$y=\frac{1}{5}x$

That implies, for x=9.

$\begin{gathered} y=\frac{1}{5}(9) \\ y=\frac{9}{5} \\ y=1.8 \end{gathered}$

Hence,

$y=1.8$