I am really pleased. (I think many of the students are too.)
Started right out with the Pooch Cafe cartoon where Pooch says the average person spends six months of his or her life waiting for a red light – asking if it was believable. The 20 people in the class worked in pairs. (We’ve started out in a classroom, not in the Mac Lab where people can hind behind the monitors. I hope to have established good classroom dynamics that will carry over when we have to move to do Excel.)
I’d intended to take attendance while they worked, but the room was so noisy with good activity I didn’t want to interrupt.
When we reconvened (after about 15 minutes) I asked the class for their answers, and got 6 answers in the range of 2 to 10 months per lifetime. Those are all in the six month ballpark. I was surprised that most of the class wasn’t surprised that Pooch had the right order of magnitude – when I first saw the problem I thought 6 months was a dramatic overestimate. (I noted that 6 answers from a class of about 20 people working in pairs meant that about 40% of the class hadn’t done the work …)
I wrote out a collective solution, starting with ingredients
- length of a lifetime, in years
- number of lights stopped at per day
- average length of a red light delay in minutes
It was clear from class participation that each of these was best expressed as a range rather than as a particular value.
That called for a discussion of units (make sure you write them along with the numbers) and of assumptions, which should be made explicit – for example, are these red lights counted only for drivers, or do passengers count them too (probably, since Pooch is a passenger in the cartoon)?
All that’s left to do is to convert lights/day to months/lifetime, using the ingredients above and the conversion factors for time, all rounded to make the arithmetic easier – for example, 25 hours/day, 10 months/year.
Plan for Thursday.
Hope they’ve started on homework problems, so have questions
Ask about number of seconds alive – scientific notation, perhaps the google calculator. That will work if someone in the class has a smartphone.
I wonder if anyone from the class will follow the link from the course home page to this blog. (If you see this you could leave a comment.)
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