Hey, it's Walk/Bike to Work Day tomorrow. And in honor of that, here's a little math problem to keep you occupied, courtesy of Guesstimation: Solving the World's Problems on the Back of a Cocktail Napkin by Lawrence Weinstein and John Adam.
"What are the relative costs of fuel (per kilometer or per mile) of New York City bicycle rickshaws (human-pedaled taxis) and of automobiles?"
You might need a few hints.
What'd you get? Post your answer as a comment. Once a few folks post answers, I'll post the one from the book, as well as the "work."