Question

Write the direct linear variation equation for the relationship:

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

A.
y = 3x

B.
y = x + 8

C.
y= 1/3x

D.
y = x – 8

Answer 1

I think it is C or D, not sure. I need help,

Answer 2

Direct linear variation means that you can express the relationship between \(x\) and \(y\) as \[y = kx\] for some constant value of \(k\) (called the proportionality constant or constant of variation).

You know a value of \(y\), and you know the associated value of \(x\). Plug them into the template I gave you to find the value of \(k\).

Answer 3

Thank you, whpalmer4! I was confused.....XD

Answer 4

So what's your answer, now that you're no longer confused? :-)

Answer 5

C did seem correct, but so did D. Ok, C is the correct answer. Nope, no longer confused! I get it now.

Answer 6

Hang on a sec, I'll show you a graph of all 4 equations.

Answer 7

Ok, but I did get the correct answer, right?

Answer 8

C. Because, when I solved it your way, I got 0.3333333 which is 1/3

Answer 9

You can see that actually two of the lines are proportional between \(x\) and \(y\), but only one of those lines has \(y=4\) when \(x = 12\).

Answer 10

Yes, C is the correct answer.

Answer 11

Thank you! Best answer I could've got, that helped my understanding!

Answer 12

Those are the only sorts of answers worth giving, in my opinion :-)