“Mastering Math for the Building Trades”, by James Gerhart

Gerhart, James. Mastering Math for the Building Trades. New York: McGraw-Hill, 2000. Print.

I grabbed this off the library shelf thinking ‘Great!  Real-world math to motivate my students!’.  I’m teaching Grade 9 this year, which is the last year that involves much in the way of Measurement – in this case, surface area and volume of three-dimensional shapes (pyramids, prisms, spheres, and cones), and the well-known Pythagorean Theorem.  I figured good old Pythagoras would show up in the slopes of roofs – which I know should be called the pitch of the roof when you’re a builder and not a math teacher.

So, after skimming the introduction, I got to page 19, which talked about problem-solving using steel squares.  After setting up the idea of roof rafters and that a rafter is the hypotenuse, it then surprised me by saying this:

“The first step in solving this problem and others like it is to reduce the dimensions to a size or proportion that will fit inside the steel square.  This is accomplished with the use of ratios”.  After explaining how to use ratios to reduce the sizes of the rise (height of the roof) and run (width of the roof), it continues “… set the unit of run on the tongue of the steel square and the unit of rise on the body of the steel square.  After setting the steel square on the edge of a board and lining up the appropriate marks… draw lines down from these lines onto the board.  The measurement of these two marks is the length of the triangle’s hypotenuse”.  Then, of course, you use ratios to scale the measurement up again.

I was flabbergasted by this, enough to ask my father if this was how builders did it, and he confirmed that they do.  I guess a calculator doesn’t show up in toolboxes very often!

That was enough for me to temporarily shelve the book, and I find that I have now renewed it twice and it has to go back to the library tomorrow.  I guess if I haven’t gotten back to it in nine weeks, I’m not likely to.  I suppose what I really learned from the book, though, is that I haven’t gotten over my preconceived notions yet, and that I should work on that before looking for real-world math to introduce into my classroom.

In better news, though, I did have my students measuring cans of food in class yesterday!