Q&A #3572

Teachers' Lounge Discussion: Logarithmic functions

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From: Susan Socha

To: Teacher2Teacher Public Discussion
Date: 2000080221:21:37
Subject: Logarithms

I love teaching logs.  I agree with the answers that were given about
remembering that a log is an exponent.  When I begin logs, I start
with 10^0 = 1, 10^1=10, 10^2=100.  Then I ask the kids 10 to what
power would equal 8?  They figure out that it is between 0 and 1, and
I have them use their calculators and guess and test until they get it
really close to 8.  Then I give them a whole bunch of numbers like 26,
121,  2345,  12876   etc. and have them guess and test until they get
the power for 10 that makes it equal to the target number.  They find
this tedious, but that's ok, because then when you tell them to press
log 2345 and they automatically get the exponent, it drives home the
lesson of exactly what a log is!  They scream why didn't you tell us
before, and all kinds of stuff, but the point has been made.  

Then move on to exponents with a base of 2.  They will try to use the
same button, or ask you where the log for base 2 button is on the
calculator.  Have them guess and test a little, and then move into the
change of base rules.  They really see the point of them if you
progress in this fashion.

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