Teaching math

— Teaching Math 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?

Teaching Math 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?

Teaching Math 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?

Teaching Math 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.

Teaching Math 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 participation after answering the question:
How did the forest birds and squirrels feel as the logger cut down the
trees? There are no wrong answers.

Teaching Math in 2000: A logger sells a truckload of lumber
for $100. His cost of production is $120. How does Arthur Andersen
determine that his profit margin is $60?

Thanks to my esteemed brother Eric for supplying this item.