I love Dan Meyer's Algebra curriculum and education blog, and have been trying to work more on integrating realistic, real-life problems into my curriculum. Here's an extra credit problem I gave today:
A man shows up at a hospital with a high blood alcohol content (the % of his blood made of alcohol). His friend tells the doctor that he had 100ml of vodka (40% alcohol), as well as 300ml of wine (12.5% alcohol). What is his blood alcohol level? Hint: there are 5600ml of blood in the human body, and blood is normally 0% alcohol. Assume that any alcohol consumed goes directly to the bloodstream.
Leave your answer in the comments.