Embellishment ....

I wrote:
=RATE(6,, -10, 100)
That is the average __quarterly__ rate.

I should have noted that that is the same as
(100/10)^(1/6) - 1.

If you want the effective __annual__ rate, ostensibly,
it might be:
=FV(RATE(6,, -10, 100), 4,, -1) - 1

I should have written "it __is__", not "ostensibly it might
be". I was thinking of how financial engineers annualize
the std dev, not the average.

Also, I might have noted that the above FV() function
can be simplified to:

=RATE(6/4,, -10, 100)

which is the same as (1 + r)^4 - 1, where "r" is the
quarterly rate, however you want to compute it.

..... Which, in your case, can be simplified to:

(100/10)^(4/6) - 1