how many cubic feet of portland are in a properly mixed yard (27 cu ft) of six sack/yard concrete?

Question

i'm building a retaining wall out of concrete and concrete suppliers reccomend a six sack per yard mix.

Answer 1

a six bag mix contains six bags (94 or 100 lb) of portland per yard

Answer 2

Cement comprises from 10 to 15 percent of the concrete mix, by volume. A minimum cement content of 6 bags per cubic yard of concrete. Here is a link that will explain concrete in detail.
http://www.cement.org/basics/concretebasics_faqs.asp

Answer 3

I would have thought 2.7cu.ft. (for a normal concrete mix of 1:3:6)