The trip on the T wasn’t slow enough for me to grade all the papers, so I can’t return them until next week.
Several students had a better way to solve the Johnny’s problem than mine – starting from 2,000,000 matzoh balls and seeing where that led, rather than trying to estimate the number of matzoh balls. Their strategy is the right one (easiest) for verification – Fermi, of course, was estimating from scratch.
Plan for today – do that, with google to convert dollars per 20 years to dollars per day. (fake matzoh balls). Then gas prices in Europe.
So I’m finishing the units chapter, and on to percentages. The bridge will be thinking of (many) units as rates. (Note to self – in chapter on linear equations, should explain power as the slope of the line that shows energy use as a function of time.)
I did most of what I planned – started with working Johnny’s back from 2 million, tricking the google calculator to do the work. Told them a little about Fermi (none had heard of him).
Converted euros/liter to dollars per gallon both by setting up the unit conversions explicitly and by invoking the google calculator. Got in a little preview of percentages – better to say gas is twice as expensive in Europe (relative change) rather than $4/gallon more (absolute change).
The last fifteen minutes was a discussion of the morality/politics/economics of tax policy. Do/should tax laws encourage the use of public transportation or driving? Do/should they encourage buying a house or renting? Do/should they discourage smoking?
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