Given:
x varies directly with y, and x=6 when y=8
Required:
We need to find the value of x when y =18.
Explanation:
if x varies directly as y the equation of variation is expressed as follows.
[tex]y=kx[/tex]Substitute x =6 and y =8 in the equation to find teh value of k.
[tex]8=k(6)[/tex]Divide both sides by 6.
[tex]\frac{8}{6}=\frac{k(6)}{6}[/tex][tex]\frac{4}{3}=k[/tex]We get k =4/3.
The equation is
[tex]y=\frac{4}{3}x[/tex]Substitute y =18 in the equation to find the value of x.
[tex]18=\frac{4}{3}x[/tex]Divide both sides by 3/4.
[tex]18\times\frac{3}{4}=\frac{4}{3}x\times\frac{3}{4}[/tex][tex]13.5=x[/tex]We get x =13.5
Final answer:
[tex]x=13.5\text{ when y =18.}[/tex]
