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 of lumber for a set of money. The cardinality of set is 100.  Each element is worth one dollar.  Make 100 dots representing the elements of the set.  The set & the cost of production contains 20 fewer points than set.
Represent the set as a subset of and answer the following question:   What is the cardinality of the set 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 2002:
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?

Teaching Math in 2010:
El hachero vende un camion carga por $100.
La cuesta de production es......