About this blog. One student left a comment on yesterday’s entry (“yesterday” is Tuesday since today is Thursday and the class meets TTh). In class I found out another had visited. Maybe more will. Maybe some will even find it helpful.

Between a quarter and a third of the class today wasn’t there yesterday, I worried/wondered whether that would be a problem since I couldn’t fairly assume I could move on from last time. I think it worked anyway.

After some administrative nonsense I handed out two of the homework problems to get started on. The first was the bumper sticker

Exercise 1.8.2. [U]  A bumper sticker available in 2007 at http://donnellycolt.com claims 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?

I told the class the [U] meant “untested” – I’ve never assigned this exercise. Tom and I walked around the room helping groups of 2 or 3 students tackle the question. Two interesting observations. One student said she’d just try to google the answer (if she could, but couldn’t in the classroom) – and was that legal? Answer (for the whole class): “yes”. The course is supposed to model the quantitative part of life, where any tool that helps you is OK. The second observation makes me wonder … one student was multiplying 42,000 by 24 as part of his work. I suggested that he round to 40*25, do 4 * 25 in his head and then tack on the four zeroes. He understood the zeroes part but said he couldn’t multiply 4*25 without writing it out on paper. I discovered (unsurprisingly) that he knew four quarters made a dollar, that a quarter was 25 pennies and a dollar 100 – but still said he couldn’t do the multiplication without writing it down.

• The author of the bumper sticker is making a political statement. We want to know if he made up (or exaggerated) the numbers he used in his (implicit) argument.

• “Can we use google?” came up as a question. The answer is “yes if you have access, but it’s also useful to see how far you can get without it.

• Every interesting question has the same answer: “it depends”. Questions with more definite answers aren’t interesting (though they may be useful or necessary).

• The Google calculator does unit conversions: asking for$700,000 per minute in dollars per year tells us 3.68164136 × 10¹¹ U.S. dollars per year. Throw away the spurious precision and put in the zeroes and you get $370 trillion.
• Without more information, you can claim that’s reasonable if you think about what the US spends is a year – the Federal budget is about 2.5 trillion dollars and the defense share is about 1/5 of that, or $500 trillion. That suggests that the bumper sticker underestimates. Google says that worldwide expenditure on war is about $2 trillion. That’s about six times what the bumper sticker claims, so its author could have made a more dramatic comparison without lying.

The class is to turn in answers to this exercise even though we started it in class. Students who visit this blog will have a leg up on part of it. They should credit this source, of course.

Looking forward to tomorrow (i.e. Tuesday).