Question

If x and y vary directly, and x = 10 when y = 3, what will be the value of x when y = 9?

Answer 1

Y=3 x=10
  X3    X3
y=9  x=30

Answer 2

Answer:  The required value of x is 30.

Step-by-step explanation:  Given that the variables x and y varies directly. And, x = 10 when y = 3.

We are to find the value of x when y = 9.

Given that x and y varies directly. So, we have

$y\propto x\\\\\Rightarrow y=px,~~~~~~~~~~~\textup{[where p is the proportionality constant]}.$

When x = 10, y = 3, then

$3=p\times10\\\\\Rightarrow p=\dfrac{3}{10}.$

So, the relation between x and y will be

$y=\dfrac{3}{10}x\\\\\Rightarrow x=\dfrac{10}{3}y.$

Therefore, when y = 9, then

$x=\dfrac{10}{3}\times9=30.$

Thus, the required value of x is 30.