Complementary Good or Substitute Good | Which of the following combinations of goods are complements and which are substitutes?

Which of the following combinations of goods are complements and which are substitutes?
Can they be either in different circumstances? Discuss.

a.  a mathematics class and an economics class

b.  tennis balls and a tennis racket

c.  steak and lobster

d.  a plane trip and a train trip to the same destination

e.  bacon and eggs

ANSWER  

a.  a mathematics class and an economics class

If the math class and the economics class do not conflict in scheduling, then the classes could be either complements or substitutes. Math is important for understanding economics, and economics can motivate mathematics, so the classes could be complements. If the classes conflict or the student has room for only one in his schedule, they are substitutes.

b.  tennis balls and a tennis racket

Tennis balls and a tennis racket are both needed to play tennis, thus they are complements.

c.  steak and lobster

Foods can both complement and substitute for each other. Steak and lobster can be substitutes, as when they are listed as separate items on a menu. However, they can also function as complements because they are often served together.

d.  a plane trip and a train trip to the same destination

Two modes of transportation between the same two points are substitutes for one another.

e.  bacon and eggs

Bacon and eggs are often eaten together and are complementary goods in that case. However, in relation to something else, such as pancakes, bacon and eggs can function as substitutes.