John decides to use the method of proportions and similar
triangles to find the height of a tree. He measures the length of the
tree's shadow and finds it is 51 feet long. Then he holds a 12-inch
ruler perpendicular to the ground and finds that it casts an 18-inch
shadow. How tall is the tree?
a. 3 ft c. 76.5 ft
b. 34 ft d. 204 ft