How come when you open up a Banana?!

Here ya go ::

There is a protective outer layer (a peel or skin) with numerous long, thin strings (the phloem bundles), which run lengthwise between the skin and the edible inner portion. The inner part of the common yellow dessert variety splits easily lengthwise into three sections that correspond to the inner portions of the three carpels.

http://en.wikipedia.org/wiki/Banana
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It doesn't always open in three ways. Maybe you just do it weird each time.

not if you uses an axe

it depends on how you do it.. its not.always 3ways :)