Reference Topics 5-7

Clock arithmetic and modular arithmetic
http://www.shodor.org/interactivate/discussions/morerem.html

This site gives a nice introduction to modular arithmetic.
http://betterexplained.com/articles/fun-with-modular-arithmetic/

Is there really such a thing as “infinity”?
http://www.math.toronto.edu/mathnet/plain/answers/infinity.html