In 1950:
A logger sells a truckload of lumber for $100. His cost of production is 4/5 of the price. What is his profit?

In 1960:
A logger sells a truckload of lumber for $100. His cost of production is 4/5 of the price, or $80. What is his profit?

In 1970:
A logger exchanges a set "L" of lumber for a set "M" of money. The cardinality of set "M" is 100. Each element is worth one dollar. Make 100 dots representing the elements of the set "M". The set "C", the cost of production contains 20 fewer points than set "M". Represent the set "C" as a subset of set "M" and answer the following question: What is the cardinality of the set "P" of profits?

In 1980:
A logger sells a truckload of lumber for $100. His cost of production is $80 and his profit is $20. Your assignment: Underline the number 20.

In 1990:
By cutting down beautiful forest trees, the logger makes $20. What do you think of this way of making a living? Topic for class discussion: How did the owls and squirrels feel as the logger cut down the trees? There are no wrong answers.