Teaching Math in 1950: A logger sells a truckload of lumber for $100. His cost of production is 4/5 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 …