39. A 6-ft-tall indoor holiday tree needs four strings of lights to decorate it. How many strings of lights are needed for an outdoor tree that is 30 ft high? (Thanks for the idea to Charlotte Chell, Carthage College, Kenosha, Wisconsin.)
39.
The lights are strung around the outside of the tree branches, so in effect they cover the outside “area” of the tree (thought of as a cone). Hence, the number of strings needed grows in proportion to the square of the height: a 30-ft tree will need times as many strings as a 6-ft tree. However, you could also argue that a 30-ft tree is meant to be viewed from farther away, so that stringing the lights farther apart on the 30-ft tree would produce the same effect as with the shorter tree.