Class 1 Tuesday, Sep 2 2014

Well I remembered the password for this blog. That’s a good start for the semester. …

Plan today: meet the students, tell them for the first time that this won’t be like any other math course they’ve taken. It will take a while for them to believe that.

Set them to work on two exercises from the text, with instructions to get as far as possible without a calculator, and as far as possible without the internet.

Exercise 1.8.2.
A bumper sticker available in 2007 at claimed that

Every Minute the World Spends $700,000 on War While 30 children Die of Hunger & Inadequate
Health Care
Are the figures $700,000 and 30 children believable?
Your answer should be a few paragraphs combining information you find on the web (cite your sources – how
do you know they are reliable) and a little arithmetic.


Exercise 1.8.8.

Spoons around the world.
According to the website, Americans throw out enough plastic utensils (knives, forks,
and spoons) every year to circle the equator 300 times.
(a) Use the information stated at the beginning of the problem to estimate the average number of plastic
utensils each person throws out each year.
(b) Is the assertion reasonable?

Here’s what happened.

Putting aside the fact that I think I talked too much, the class went well. I managed to make (and I think convey) a few important points for the course.

Just reading the words is important.

To deal with $700,000 per minute it’s useful to convert to $/year. We did that by finding minutes/year with curly arithmetic. There are about 60*25 ~ 150 minutes/day (rounding the 24 hours up to 25 to make the arithmetic easy) and 400 minutes/year (365 is a really ugly number) so about 600,000 minutes per year. That’s an overestimate – round down to 500,000 minutes per year. (The Google calculator says 525949.) That means 35 (10 zeroes) or 350 billion dollars per year. Then a student said that was too low – that  US military spending alone was trillions of dollars per year. I asked him how he knew, and he said he was a political science student familiar with the federal budget. I let that go, since I wanted to encourage the students to bring outside knowledge to bear. But writing this I decided to check. Wikipedia – probably reliable in this instance – says $600 billion per year for the US.( That still makes the bumper sticker too low by half, just for the US. The same wikipedia page gives $12.6 trillion (for 2013) for the whole world. I should probably revisit this on Thursday. (I wonder if any students will read about it here.)

The questions “Is $700,000/minute reasonable?” has two interpretations. First, does it make sense all by itself – is it the right order of magnitude (ballpark, number of zeroes)? Second, is it reasonable in the political context intended by the person who wrote the bumpe rsticker – s/he wants us to answer “no” – that money should/could  be spent to reduce child mortality.

Spent some time on 30 children dying per minute. Students used the web to discover that figure is in fact of the right order of magnitude.



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