[TIPS] - three math sites

Three math sites today! Woohoo!!

 

This one is a very simple math challenge for kids in grades 6 and up, I would guess. The challenge :

You have fifteen seconds. Using standard math notation, English words, or both, name a single whole number-not an infinity-on a blank index card. Be precise enough for any reasonable modern mathematician to determine exactly what number you've named, by consulting only your card and, if necessary, the published literature.

http://www.scottaaronson.com/writings/bignumbers.html

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A repeat (by request) What's Unique about this number?

 

http://www.stetson.edu/~efriedma/numbers.html

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And finally, Inner Algebra, or "How to Solve Algebra Problems in Your Head"

http://hilomath.com/inneralgebra/html/node13.html