(snipped)
Sorry but your description of a ream is not true.
A ream is a specific number of sheets and has nothing to do with the
weight of the paper. A ream is 20 quires (look that up!).
Like many measures there have been some variations over the years. The
current definition of a ream of paper standard for printing and copying
is 500 sheets. There is also a Printer Ream (a few sheets more
probably an allowance for testing) and some other definitions, but they
are all about 20 quires
Occasionally one will see the term "Ream" used inappropriately,
sometimes because of ignorance, sometimes in an attempt to cheat the
public.
