So simple a caveman could do it...

[dawn_of_change]

*Teaching Math In 1950*
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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*
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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*
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A logger sells a truckload of lumber for $100. His cost of
production is $80. Did he make a profit?

*Teaching Math In 1980*
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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*
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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 2005*
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El hachero vende un camion carga por $100. La cuesta de
production es.............