Math for Knitters - Calculating Yardage on a Partial Ball of Yarn

You have a partial ball of leftover yarn...is it enough for the project you want to make? Here's how to calculate the yardage of that partial ball. If you have a video suggestion for the Math for Knitters Series, please leave me a comment or drop me a note at staci@verypink.com. The sweater on the mannequin is my Woman's Zippered Letterman's Jacket, pattern + video tutorial: http://verypink.com/2011/09/07/womans-zippered-lettermans-jacket/ The pattern for the sweater I'm wearing can be found here (not my design): http://www.ravelry.com/patterns/library/sitcom-chic The nail polish I'm wearing is Julep color "Flora": http://www.julep.com/rewardsref/index/refer/id/683913/