Area and Perimeter -- Rectangular City Planning (January 18-20)

We explored how the children identified a rectangle on a geoboard.  The children learned the most general attibute is a "polygon," "quadrilateral,"  a "parallelogram," then a "rectangle." 'How do you name this rectangle?' was the next question. We learned that you name rectangles by their dimensions.  Two dimensions, "length and width," "base and height." For example, a 3x5 rectangle.

The problem was that when the children tried to count the dimensions, they counted the pegs on the geoboard or the vertices (corners) giving them the wrong dimensions by over-counting one on each dimension. I had the touch the sides of each unit with their finger, or better, a pencil point slow enough not to double or under count.

Then one of the children says 15.  15 what? "Square Units."  Then we traced out each of the 15 square units to make square units come alive.  I explain that this is called "area," and then we look at other things in the room that represent "area" like the floor, walls, ceiling, surface of anything including their skin.

Then one student says 16.  16 what?  The "outside," they said. Yes, the "perimeter." Then the children noticed that two times one dimension plus two times the other dimension is a faster way of calculating the perimeter (3+3+5+5).

The attached pdf has an exercise that most of the children worked on where I designed four different airal views of a city with rectangular buildings.  Their objective is to calculate the area and perimeter of each building. I recommended that the 2nd through 5th graders then add the total area in square units and then add the total perimeter in units.  The Ks and 1st graders should just calculate all of the individual area and perimeter numbers. The answer key follows each city challenge.

Now for the creative part.  The last two pages of the pdf gives the children the opportunity to create their own cities and make the calculations of area and perimeter.