SOLUTION: Suppose y varies directly as x and that y=21 when x=3. Find the value of y when x=5.

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equation Customizable Word Problems -> SOLUTION: Suppose y varies directly as x and that y=21 when x=3. Find the value of y when x=5.      Log On


   



Question 134116: Suppose y varies directly as x and that y=21 when x=3. Find the value of y when x=5.
Answer by jojo14344(1513) About Me  (Show Source):
You can put this solution on YOUR website!
By Ratio and Proportion;
1st condition; x=3 and y=21
2nd condition; x=5 and y=?
so,
3/21 = 5/y
y = 5 * 21 /3
y = 35
It is just right to be y=35 (as shown by ratio above)as it varies directly to x.
When x goes up, so does y goes up!