Q&A #5442

Teachers' Lounge Discussion: Percentage of change

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From: Michelle

To: Teacher2Teacher Public Discussion
Date: 2002011414:06:57
Subject: Calculating percents

In the adult education program in which I teach, I see students all
the time who've never been able to remember, and therefore, apply the
strategies for solving percents based on algebraic equations, i.e. A x
B/100 = C  

Instead, I teach them to use proportion setups to solve percent
questions. Since we use proportions to solve many other types of
questions for which they're studying, it's a natural complement.
The basic setup is this   A / 100 =  B / C, with 100 always
representing the whole in terms of percentage and A or C being the
corresponding percent. (one can line up the % top and bottom or side
to side, as long as the other numbers correspond correctly)

 From that basis, I go on to teach them to use this framework to solve
different types of questions using logic rather than memorization.
100% represents the whole, the original number (price), etc. The other
percentage represents the part, the sale price, the discount, etc. It
requires teaching them to think hard about what they are looking for
and to use mental math. For example, if they are given the discount,
but looking for the sale price, they need to calculate the sale price

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