What is the direct linear variation equation for the relationship?

y varies directly with x and y = 4 when x = 12.

A.
y = 1/3x

B.
y = x + 8

C.
y = x – 8

D.
y = 3x

Question

What is the direct linear variation equation for the relationship?
 
y varies directly with x and y = 4 when x = 12.
 
 A. 
y = 1/3x
 
 B.
y = x + 8
 
 C.
y = x – 8
 
 D.
y = 3x

photon336 · Answer

It's in the form  $$y = k*x $$

anonymous · Answer

A.
Solve 4 = k * 12

mysticfury · Answer

yes, but when i plug in the numbers A and C are both correct

photon336 · Answer

True, but from what I know, direct linear variation is  y = k*x

nnesha · Answer

how are you getting A and C

nnesha · Answer

how would you solve for k ?

mysticfury · Answer

so im going with A then

nnesha · Answer

remember. a/1 isn't same as 1/a

nnesha · Answer

$$\large\rm 4=k *12$$
divide both sides by 12 to solve for k(constant of variation ) $$\frac{4}{12}=k$$ simplify the fraction

nnesha · Answer

or the other way around 
as mentioned above equation for direct variation is y=kx
substitute in y and x values for both option A and C 
$$4= \frac{1}{3} \cdot 12 $$ 
$$4=3\cdot 12$$
which one is true ?