When I use one of the skeins of RH or similarly priced yarn I usually stand it up in a small wastebasket or coffee can or whatever and work from the outside. I don't have to deal with yarn barf and I don't have the skein collapsing and making a tangled mess to deal with. When it gets down small enough I will wind it from the middle, somehow it's not as messy to do so at that point. Do whatever works best for you. I got sick and tired of that yarn barf and the tangled collapse mess sometime after the first half is used up.
I should never overestimate my basic arithmetic skills.