SOLUTION: If x and y vary directly, and x=10 when y=3, what will be the value of x when y=9??

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: If x and y vary directly, and x=10 when y=3, what will be the value of x when y=9??      Log On


   

Question 1091802: If x and y vary directly, and x=10 when y=3, what will be the value of x when y=9??
Found 2 solutions by Edwin McCravy, MathLover1:
Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!

If x and y vary directly,
x=ky
and x=10 when y=3,
x=ky
10=k3
10%2F3=k
Substituting for k in

x=ky
x=expr%2810%2F3%29y

what will be the value of x when y=9??
Substitute 9 for y in

x=expr%2810%2F3%29y
x=expr%2810%2F3%29%289%29

x=expr%2810%2Fcross%283%29%29%28%22%22%5E3cross%289%29%29

x=30

Edwin

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

If x and y vary directly, we have
y=kx
and if x=10 when y=3,we can use it to find k
3=k%2A10
k=3%2F10
k=0.3
so, equation is:y=0.3x
the the value of x when y=9 is:
9=0.3x
9%2F0.3=x
x=30