23 million Dollar Books, Pricing Algorithms Compete on Amazon

Found this great story as a hook for exponential functions:

http://www.michaeleisen.org/blog/?p=358

Basically a book called "the Making of a Fly" reached over 23 million dollars in cost when the pricing algorithms for two companies continuous competed with each other. Michael Eisen caught some of the prices over a few days and figured out the ratio between them:

Here is a current pricing of the book:

ZD Net also found some great screen shots to help tell the story. Its perfect for exponential growth:

Jeff Bezos and Negative Orders on Amazon

When Amazon first started, you could order a negative quantity of books.

See here at: https://www.youtube.com/watch?v=-hxX_Q5CnaA&feature=youtu.be&t=43s

Perfect hook for negative numbers. Thanks Jeff!

Full video here:
 

Counterfeit Money Problem

I came across this great problem and am thinking of using it to demonstrate the power of using a physical model in solving a math problem:

http://www.nctm.org/publications/blog/blog.aspx?id=42693&blogid=599514

and the answer:

http://www.nctm.org/publications/blog/blog.aspx?id=42820&blogid=599514