Andrew and I began a new chapter today. We started by drawing an quadrilateral and splitting it into 2 triangles. I asked Andrew what the sum of the angles in 1 triangle are, he answered 180 degrees. So then I asked him since the quadrilateral is comprised of 2 triangles, how many degrees do you think it has? We discussed that since 180+180=360 , the interior angle sum must also be 360. We tried it again with a pentagon. We saw that it could be cut into 3 triangles, each at 180 degrees so the interior sum must be 180(3)=540 degrees. Then I showed Andrew that there is a formula we can use to determine the interior sums, without having to cut them into triangles each time. We can use 180(n-2). We used it to answer the sum of the interior angles of a decagon (10 sides). We got 180(10-2)=180(8)=1440. Andrew seemed to pick up on this concept easily.