Question

Using the shadow method, Norman finds the height of a tree as follows: He measures the shadow of the measuring stick (4ft) and the tree (20ft). He then uses similar triangles to find the tree's height.

If the measuring stick is 3 feet long, how tall is the tree?

4 feet squared + 20 feet squared = c squared

Answer 1

No hypotenuse is necessary. We are looking at corresponding sides of similar triangles here
3/4 = h/20
so
4 h = 4 * 5 *3
h = 15

Answer 2

Here is a picture of a similar (no pun intended) problem
http://mathforum.org/sanders/connectinggeometry/ch_09Similar.html