What makes a person educated?Education remains a concept as difficult to define and as open to debate as it is essential to our identity. Is a...

This is a wonderful question.  I would distinguish between
formal education and informal education.  I would also distinguish between education and
wisdom.  These two distinctions cover the situations that you mention
here.

The grandmother is not educated.  She does not have
any (from what you say) of the knowledge that comes with education.  She would not, for
example, be able to do algebra or explain the idea of supply and demand.  However, she
is probably wise.  That is, she knows what is approprite to do in various life
situations that she has ecountered.  This is very important, but it is not
education.

Bill Gates has more education than his
ex-classmates in certain areas.  True, he did not learn these things in school, but he
did learn them informally.  Education is the acquisition of knowledge and he has
acquired knowledge on a relatively broad range of subjects (computers, business,
management, things having to do with his foundation).  It is informal education because
he did not gain it in school, but it is still
education.

Education, then, is the acquisition of
knowledge.  It can be formal or informal, but it is not the same thing as the wisdom
that comes with experience and age.