Messages written in Japnese are not sometimes properply displayed
through Google posting.  So that I would like to swich to English. 
Forgive me this inconvenience, and I hope that the reader has no
difficulty in understanding what I shall write in the following.


[Quiz] 

A certain writer, just like the_Stupid_GON, is known to make spelling
mistakes
at the average of one word for each twenty pages of his manuscripts.

Now suppose that this writer has completed writing one hundred pages
of
manuscript.

What is the probability that this manuscript contains more than five
spelling
mistakes ?