Plan: Begin introducing explicit computation with units. Try not to lose the connection to Fermi problems. I wonder if I can find a way to have them work in small groups and still learn the new techniques. Ask for a blackboard presentation of results, with units written out? To do that the problems have to be pretty straightforward.
What I did: Started with the Larrick-Soll example from Chapter 2 – upgrading from 12 mpg to 14 mpg saves more gas than upgrading from 28 to 40 mpg.( Saves more money too, but the computation is really independent of the price of gasoline.) Naturally, that wasn’t what people thought would happen. Then I did cost of gasoline in France.
I concentrated on the importance of writing the words for the units before writing the numbers. From the looks on their faces I think three (perhaps four) students actually believed me and will try to learn to do it. The rest are likely to resort to old strategies e.g “is it bigger or smaller?” , or will just guess and hope to be right.
I didn’t have time to do any group work. I think that might be a mistake. I promise I will plan a Thursday class that allows for some.
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