Thursday, March 14, 2013

Day 112: Area & Perimeter

Today was partially lost to more (optional for our school) standardized testing, so the Unit 7 Assessment had to be moved to Monday. I generally hate Monday assessments, but in order to get Unit 8 fit in before spring break, sacrifices must be made. 

The only topic left in Unit 7 is area & perimeter of quadrilaterals  so I used Geogebra to show how we can find shortcuts to solve for the area of various shapes. I don't bother with formulas for perimeter - as long as students understand what perimeter is (and how to use the Pythagorean Theorem to solve for diagonal distances), I assume they'll be able to figure it out. 

In general, our theme for finding area is based around the idea of making a rectangle either from the quadrilateral directly (parallelogram), or making the rectangle around the shape and noticing that it's area is double the shape's area. 

In my head, understanding how to determine area is more useful than memorizing a bunch of area formulas, but students are unfamiliar with a general approach and generally feel more comfortable with the formulas. Except, most students cannot reliably use a formula as a result of very weak algebra skills. Or, they lack the ability to differentiate horizontal/vertical distances on a graph from diagonal lengths. Or they have no idea how to identify a base and a height.

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