Commuting students. At a well-known university ¼ of the undergraduate students commute, and 1/3 of the graduate students commute. One-tenth of the undergraduate students drive more than 40 miles daily, and 1/6 of the graduate students drive more than 40 miles daily. If there are twice as many undergraduate students as there are graduate students, then what fraction of the commuters drive more than 40 miles daily?
See link. This exact problem was solved there.
http://www.jiskha.com/display.cgi?id=1236980230