How can we determine the area of a trapezoid?

Today we were exploring the area of trapezoids. I let the students explore this concept for awhile, but we struggled today, as this is a very hard shape to determine area for. With minimal guidance, we did it together.

We know that last week we worked with parallelograms and that the formula for area of that was base x height. From there, we were able to see that we could make a parallelogram from 2 trapezoids. Then we could use the formula base x height, but this time we had 2 bases to add. So the formula starts with (B1 + B2) x height. Then I had a few friends say, we need to divide by 2. I asked why, they told me because we are finding the area of 1 trapezoid, not 2. So even though I helped a little, once they got started...they couldn't be stopped!!

Our finished area chart!!