There is a bridge and four people need to make it across?

First take Sarah (7) and Nick (5) across the bridge. Then, bring Nick back (takes 12 min). Then bring the colonel champ and Charles across (20 min). Add 20 and 12 and you get 32 min. Then bring Sarah back to where nick is (39 min). Finally, both Nick and Sarah cross the bridge together (46 min). Thus, the least amount of minutes is 46.