Parallel Lines are Where?

  As you know by know, I'm always looking for places math is used in real life so as to show students it is practical.  Usually, I look for connections in Algebra I or II but today, I'm looking at parallel lines which appear in those two plus Geometry.

We teach parallel lines as lines that never cross. The lines have the same slope but different y intercepts.  Do we really take time to really discuss when students will see these in real life or why its important to know how to find them?

Look at the picture, they are railroad tracks which have to be parallel because the distance between wheels will never change.  If the tracks are not parallel, the trains will derail and it could cost the company millions of dollars.  What about all the lanes on the roads or highways?  Those lines have to be parallel so none of the cars will get close enough to run each other off the roads.

What about the rows of shelving in the supermarket.  Most are set up as parallel segments so as to allow enough room for carts to pass each other in each aisle.  Some of those shopping carts are getting rather wide especially the ones set up children.  The parallel shelving can be found in libraries, book stores, hardware stores and so many other places.

In addition, you can look at parking lots because there are rows up rows of parallel lines and perpendicular lines.  Even buildings have parallel and perpendicular segments which make the walls of the building.  Windows have both parallel and perpendicular segments to create the whole effect. 

It seems like every where you look you see parallel lines be it in wood flooring, brick walls, stairs, ladders, and so many other places, even on cement sidewalks.

Just think what type of brainstorming you could have the students do when starting a unit on parallel and perpendicular lines.  You could even introduce the idea when state build certain intersections, they are required to make them meet at a 90 degree angle which means they are perpendicular.  Why would the government require that?  It requires students to think about the reasons behind such a requirement. 

So many fun things to discuss when you talk about this topic.  What do you think? I'd love to hear from you all on your opinion on this topic.