Nets Math and/or You Missed Q2b


This page will address information on Nets Math as well as how to solve a problem in the aMAZEing Math Maze.  First, let's talk about poor Bob and his dilemma  concerning the mailing of a package.

Plugging in the values of length = 6" and width = 9" and height which was 4" into the equation $3.00 + ($1.20)(length + width + height) = cost - should leave you with the equation 3+(1.2)(6 + 9 + 4) = c.

Notice that I left off the $ signs and the " marks.  We know we're dealing in inches and we know we're dealing in dollars - so we can safely leave them out for now.  We needed them to be sure we weren't mixing inches with feet or dollars with cents.  I also left off the zeros in the decimal parts.  3.00 became 3 and 1.20 became 1.2.  I can do this because leading zeros in whole numbers have no effect.  Meaning 04 is the same as 4.  Trailing zeros after the decimal have no effect.  So, 3.00 dollars is the same as 3 dollars.

Now, we perform the operation inside the parenthesis first.  There is only one number in the first parenthesis, so that's done (1.2) is as good as it gets.  Now add (6 + 9 + 4) and get 19.  So, the equation looks like 3 + (1.2)(19) = c.  Now we multiply 1.2 times 19.  When parenthesis are touching like that, it means we multiply.  1.2 x 19 = 22.8.  Add the 3 to that and we get 25.8 or $25.80.  So, you should have chosen answer b)  $25.80.

What the heck - why not try again?  Or, go to one of the web sites listed at the bottom of this page.

A little about Nets Math

Take a common hollow 3-dimensional object and unfold the sides in such a way as to make a 2-dimensional object that can be folded easily back into the 3-dimensional object.  The is a subject worthy of topologists or origamists.  There are a lot better, more technical definitions to be had, but I am trying to gear everything towards Algebra 1 students (and probably failing).  

The figure above is an example of a nets.  If you fold the long end around and the top and bottom up,  You will end up with a cube.  Many standardized tests show you a variety of these figures for a lot of common 3-D shapes and want you to tell them what the folded figure would be.  

Rather than steal a bunch of diagrams from other websites, I figured it would be more ethical/legal to just re-direct you to a decent site that has a lot more examples (I made this one in MS Excel).  The National Council of Teachers of Mathematics has developed a game that works with Nets Math.

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