🚀 go-pugleaf

Gilles.Leblanc@f2.n255.z1.fidonet.org (Gilles Leblanc) writes:
>  Imagine the difficulty they would encounter 
>if they had to calculate with a pencil and paper a 7% tax (GST) on a good or 
>service and then have to add a 10 % provincial sales tax to that.

I think this is a bit of a red herring.  I agree that a student ought to
know how to do it -- i.e., that taking 7% means multiplying by 7/100,
and that that in turn means multiplying by 7 and moving the decimal point
over.  But in practice I'd sure rather use my calculator than try to
multiply by 7 out in the field if I were actually buying or selling some
good or service.  Even before calculators, I don't think anyone *really*
ever did such calculations -- instead they taped little charts to the
side of the cash register.

Instead of making kids work out such problems with pencil and paper, I'd
rather make them do instant rough estimates:  "Is 7% of $20 closer to
$1 or to $5?"  Or, "Is 7% of $1000 closer to $5 or to $50?"  The point
of the game is that you only get three seconds to answer, or maybe you
do it in competitive teams like College Bowl where the first one to answer
gets the point.  Along with this you do stuff like the paradigmatic
"how many grains of sand on the beach?"  Calculators won't interfere with
this kind of estimation work.

In article <35566.2B4B80EB@puddle.fidonet.org>, Gilles.Leblanc@f2.n255.z1.fidonet.org (Gilles Leblanc) writes:
|>  My 
|> question is whether we are harming the students by teaching them to use the 
|> tools before they have understood the concept.  I would appreciate any 
|> response to these comments.

Can you make sure they understand the concepts? You're the teacher!
Give them problems where they have to solve for the percentages or whatever
symbolically.

Sample problem:

The bank has an interest rate that varies from month to month. If I have
x in the bank in the months n, n+1, and n+2 where the interest rates are
a%, b%, and c%, how much money do I have in my account at the end of month
n+2?

-- 

Henry Choy
choy@cs.usask.ca

What rolls down stairs alone or in pairs            This has been brought to 
Rolls over your neighbor's dog?                     you by the numbers 4
What's great for a snack and fits on your back?     and 9 and the letter P.
It's Log, Log, Log!  -- "The Log Song", from            -- Big Bird
                         Ren & Stimpy

Math is tough!       -- Barbie

choy@skorpio.usask.ca (I am a terminator.) writes:
>Gilles.Leblanc@f2.n255.z1.fidonet.org (Gilles Leblanc) writes:
>|>  My 
>|> question is whether we are harming the students by teaching them to use the 
>|> tools before they have understood the concept.  I would appreciate any 
>|> response to these comments.
>
>Give them problems where they have to solve for the percentages or whatever
>symbolically.
>
>Sample problem:
>
>The bank has an interest rate that varies from month to month. If I have
>x in the bank in the months n, n+1, and n+2 where the interest rates are
>a%, b%, and c%, how much money do I have in my account at the end of month
>n+2?

This is an idea that I REALLY like.  Numbers are simply symbols and
students shouldn't be concerned with a numerical answer until the end
of the problem were they plug in the numbers.

I know of one case where students got to college and their only
concept of sine and cosine and tangent was as their teacher had told
them, ``Those buttons on the calculator.''

Mark D. Smucker    -----    mds@iastate.edu