Question

Given that y is directly proportional to x. If y = 30 and x= 5, write an equation that connects y with x.

Answer 1

Given:

y is directly proportional to x.

$y=30$ when $x=5$

To find:

The equation that connects y with x.

Solution:

It is given that, y is directly proportional to x. So,

$y\propto x$

$y=kx$                     ...(i)

Where, k is the constant of proportionality.

We have, $y=30$ when $x=5$. Substituting these values in (i), we get

$30=k(5)$

Divide both sides by 5.

$\dfrac{30}{5}=k$

$6=k$

Substituting $k=6$ in (i), we get

$y=6x$  

Therefore, the required equation is $y=6x$.