This is a short TED Talk by Rob Reid (The $8 billion iPad) that tries to infuse a little “reasonability test” into our blind belief in the numbers provided by those with self-interest … in this case, the music/entertainment industry.
There are several examples that you could turn into signed number addition or subtraction problems. In my favorite example (about 2:57 in the video), Reid uses what he calls “Copyright Math” to “prove” that by their own calculations, the job losses in the movie industry that came with the Internet must have resulted in a negative number of people employed.
In 1998, prior to the rapid adoption of the Internet, the U.S. Motion Picture and Video Industry employed 270,000 people (according to the U.S. Bureau of Labor Statistics). Today, the movie industry claims that 373,000 jobs have been lost due to the Internet.
[Intermediate Algebra] If the job market for the motion picture and video industry grew by 2% every year (without the Internet “loss” figures), how many people would be employed in 2012 in the combined movie/music industries? How many jobs would have been created between 1998 and 2012 at the 2% growth rate? If the job market grew by 5% every year (without the Internet “loss” figures), how many people would be employed in 2012 in the combined movie/music industries? How many jobs would be created between 1998 and 2012 at the 5% growth rate?