Last week a fourth grade teacher in Philly invited me to work with her students. She emailed me to explain, ”We are moving into intersecting, parallel, and perpendicular lines. Would it be possible to focus your lessons Tuesday and Wednesday around this skill?”

On Monday I was still thinking about possibilities. I was walking in South Philly and suddenly thought of taking some photos with my iPhone. Here are the photos I took that day:

I combined them from photos that I took in New York City some time ago and posted here:

http://mathforum.org/blogs/suzanne/2012/07/

I made a PDF with one photo per page, sent it to the teacher Monday late afternoon so that she could project it on Tuesday during class. Here’s how the lesson went:

After greeting the students who I’ve not seen for awhile (standardized testing prep consumed their school/teacher for quite some time), I wrote these phrases on the board:

parallel lines
perpendicular lines
intersecting lines

I asked them to talk to me — I asked them,  ”What do these phrases mean to you?” It quickly became quite clear that they knew a lot! After some time listening to them I told them that I took some photos on Monday. I further explained that I had been thinking about today’s visit and had “parallel” “perpendicular” and “intersecting” on my mind. We looked at the photos together (projected on the SMARTboard by their teacher). The photo that we really started talking about was this one:

What do you see?

In case you’d like a copy of the PDF I created and sent to the teacher, I put it here so that it’s accessible:

http://mathforum.org/alejandre/linesbig.pdf