People
appear
to
be
born
to
compute.
The
numerical
skills
of
children
develop
so
early
and
so
inexorably
that
it
is
easy
to
imagine
an
internal
clock
of
mathematical
maturity
guiding
their
growth.
Not
long
after
learning
to
walk
and
talk,
they
can
set
the
table
with
impressive
accuracy
-- one
knife,
one
spoon,
one
fork,
for
each
of
the
five
chairs.
Soon
they
are
capable
of
knowing
that
they
have
placed
five
knives,
spoons
and
forks
on
the
table,
and,
a
bit
later,
that
this
amounts
to
fifteen
pieces
of
silverware.

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