Socks come in boxes of 6 pairs. Most of the time these are sold per box. Exceptionaly, a box can be opened to sell the socks by pair. But this doesn't happen often.
In the current system (not OpenERP) a decimal can be used. So when 1 pair of socks is sold, then 0,17 x 'box of socks' is sold.
How can this be correctly handled in OpenERP?