Question 62461
A 3-foot pole casts a shadow of 9 feet.  How tall is a tree with a shadow of 12 feet?
You need to set up a proportion because these are similar triangles.
{{{x/12=3/9}}} Notice the heights numerators and the shadows are denominators.
{{{x/12=1/3}}}  Reduce where you can.
{{{12x/12=12(1/3)}}}
{{{x=12/3}}}
{{{x=4}}} ft.
Happy Calculating!!!