## anonymous one year ago if y varies directly as x and y=49 when x=7, what is the value of y when x=3? a. 7 b. 9 c. 49 d. 21

1. SolomonZelman

$$\large\color{black}{ \displaystyle y=\color{orangered}{\rm k} x}$$ this above, is the equation of a direct variation. In this equation x and y are directly proportional to y, so that you can multiply x by some constant k and obtain y. (this perfect proportion is called direct variation) it is a line with a slope k that goes through the origin.

2. SolomonZelman

If you are given that that y=49 when x=7 then you can go ahead and find the constant k. plug in 49 for y and 7 for k, into the $$\large\color{black}{ \displaystyle y=\color{orangered}{\rm k} x}$$

3. SolomonZelman

and then after plugging in solve for k

4. SolomonZelman

When you find the k, you can figure out the value of y when x=3. How? you can plug in the value of k you just found, and plug 3 instead of x. (again u r plugging into $$\large\color{black}{ \displaystyle y=\color{orangered}{\rm k} x}$$ )