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Topic: MLCS Webinar on April 24: Registration Open
Replies: 31   Last Post: Apr 12, 2012 11:45 AM

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 Phil Mahler Posts: 126 Registered: 12/6/04
Re: MLCS Webinar on April 24: Registration Open
Posted: Apr 6, 2012 7:01 AM
 att1.html (4.0 K)

OK, I¹m kind of slow sometimes, I¹d rather admit it and learn something,
so...

Why is the \$0.16 irrelevant?

I got \$132.16, using proportion and would have responded with that answer. I
understand about significant figures, and if applied to this problem
strictly speaking, would produce an answer of \$130.

Of course I agree that electric bills are not proportional to usage because
of the fixed costs, but given the question posed, I would have included the
\$0.16.

---

Regardless of what I missed above, I consider proportion to be a very
powerful tool that we do not give our students in sufficient doses.

As I have noted in the past, my universe of discussion is my developmental
students in an open-door institution. Many cannot compute area, nor solve
³you drive at 50 mph for two hours, how far have you gone², nor compute
miles per gallon... But I can probably teach most to make a table which will
allow them to solve a proverbial two-trains problem, which is what will be
in the text. So they can do two trains, without a clue about what¹s going
on, but still can¹t do one train. :-)

As for function, I wouldn¹t apply it to mpg, mph, electric bills as stated.
But I would if the electric bill question had a fixed cost also. I think (I
dare say I know) we don¹t give these students enough use of y = mx + b so
it¹s truly useful, and can be applied in other contexts, like economics, for
example ­ or electric bills.

Phil

On 4/5/12 5:04 PM, "Ed Laughbaum" <elaughba@math.ohio-state.edu> wrote:

> Guy,
>
> The \$0.16 is irrelevant. But then if I overcharged 1,000,000 customers by
> \$0.16 (or whatever it is based on usage). \$0.16 becomes significant. The point
> was that they couldn't solve a really simple problem. BTW: I failed to give
> you a second data point in the original posting. Also, my point was that all
> these highly trained people could only use what they had learned in middle
> school.
>
> This discussion may not be worth the effort because no one knows what is the
> proper approach or course or etc.
>
> Ed
> =============================
> On 4/5/2012 4:09 PM, Guy Brandenburg wrote:

>>
>> Electric bills aren't necessarily exactly proportional to the kwh used. And
>> does 16 cents really matter anyway?
>>
>> Guy
>>
>>
>> On Apr 5, 2012, at 1:27 PM, Ed Laughbaum <elaughba@math.ohio-state.edu>
>> wrote:
>> ...

>>>
>>> Relative to this post, I have observed that I often see the mathematical
>>> literacy proponents argue for proportional reasoning as a mainstay outcome.
>>> This in turn, reminded me (recall through neural associations) of an
>>> informal survey I took on several colleagues who were not in any of the STEM
>>> fields but all had a bachelors degree through a PhD. In the following
>>> "problem" everyone used proportional reasoning.
>>>
>>> If you use 1205 kWh of electricity and your bill is \$130, how much is your
>>> monthly bill if you use 1225 kWh? Everyone got \$132.16 for the answer when
>>> it is \$132.
>>>
>>> What I wonder is, if focusing on proportional reasoning will solve this very
>>> simple problem (of thinking relationships are proportional), or whether we
>>> should be focusing on function. Or something else? Of course, my opinion is
>>> on function, but it is an opinion.