Question

If y is directly proportional to x & when $x=2$ & $y=4$, what is constant of proportionality?

• A. $1$
• B. $3$
• C. $5$
• D. $2$

Answer 1

The correct option is D $2$

By definition of proportionality,

If $y$ is directly proportional to $x$,

$y$ $\alpha$ $x$

$\therefore y=Kx$ .......Equation $1$

where $K$ is constant of proprtionality

Now,

Given that $x=2,y=4$

putting the above values in Equation $1$ we get,

$4=K\times 2$

$\therefore K=2$