When we say that y varies <em>directly </em>with x, we mean that whatever value x is scaled up by, y will be scaled up by, too. The simplest kind of direct variation is one where y = x for all values of x. If you multiply x by some value, y must be multiplied by that same value.
More generally, though, you'll have something of the form y = kx, where the variable k here is referred to as the <em /><em>constant of proportionality.</em> Another way you can think of k is as the <em>ratio of y to x</em>.
In this problem, you're given a set of values for x and y, and you'll need to use those to find the constant of proportionality before you set up an equation relating x to y. Substituting our general equation y = kx for the given values, we have:
-5 = k(15)
To get k, simply divide both sides by 15 to obtain:
k = -5/15 = -1/3
So, our general equation, for <em>any x</em>, would be y = (-1/3)x
Answer:
gfjfgjyujfyuj
Step-by-step explanation:
Answer:
3rd one
Step-by-step explanation:
Answer:
Step-by-step explanation:
we know that
A relationship between two variables, x, and y, represent a proportional variation if it can be expressed in the form 
or 
so
For 
substitute
------> 
therefore
Answer:
$220
Step-by-step explanation:
5.50 ÷ 10 = .550
$.40 x 550 = $220
