math help please.

Question

Find an equation of variation in which y varies directly as x and y=1.3 when x=0.2. Then find the value of y when x=4

 

An equation of variation is y= __

 

The value of y is ___ when x=4

Answer 1

If y varies "directly" as x, it means that y is directly proportional to x, or that y is a constant multiple of x.  Those are all different ways of saying the same thing.

 

So the equation is something like y = kx, where k is some constant.

 

Since you know the value of y for some specific value of x, you just have to plug those into the above equation to find x:

 

y = kx

1.3 = k * 0.2

1.3 / 0.2 = k

6.5 = k

 

So the equation of variation is y = 6.5 x

 

When x = 4, y = 6.5 * 4 = 26