Reflection: Coherence Working Backwards with Percents - What happens when a problem is not straightforward? - Section 2: Explore


Students liked my opening statement: "the beauty of math is that the rules never change."  From that statement, I had them talk with their groups about the "equation" (I never formally introduced it as the percent equation) that we used to solve the mark up and mark down problems.  Students were able to come up with the equation: original x percent = new, with the stipulation that percent had already been compared to 100 (markup of 20% was already changed to 1.20, markdown of 20% was already changed to 0.80).  The fact that the kids were able to come up with that equation made my job today much easier.

For the notes, we simply looked at an example problem.  Underneath the problem I had written the equation that they came up with, and I instructed them to read the problem and fill in their equation as they saw fit.  Students then realized they had the "new" and not the "original."  So from there we were able to talk about inverse operations and what they do.  I did find that this method, so far, seems easier for the kids than using a proportion (which we have done every year up until now) ever was.  I have included the smartboard notes to accompany my explanation (I upload these daily on my school webpage for parents).

The biggest misconception, though at this point I think it is more carelessness, was placing the values in the wrong spots during the table challenge.  Students started hastily placing numbers in the "new" place since that was the focus of the day's lesson, instead of really reading the problem through to determine the information that they had.  I think this will come with time and practice.

  Coherence: Notes Reflection
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Working Backwards with Percents - What happens when a problem is not straightforward?

Unit 3: Percents
Lesson 11 of 21

Objective: Students will be able to work backward in a percent problem to find the original price.

Big Idea: You can apply percents - but can you work backwards to find them? This lesson gives students an opportunity to unravel percent problems.

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2013 04 23 12 06 55
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