MElizabeth wrote:
If I had invested $10,000 in 1948 and in 2006 I wound up with 4 million+
dollars, how do I figure what percentage my $10,000 made over the 58 years?

There are two correct answers, depending on what you really want to
know.

If A1 contains the original 1948 investment $10,000 and A2 contains the
value in 2006 ($4M+), the simple return is (formatted as Percentage):

=A2/A1 - 1

If you want to know the compounded annual return rate, that is:

=rate(58, 0, -A1, A2)