After a math lecture in Harvard the students went to the cafeteria and each one of them took a cup of tea and cheese sandwich. They all paid $18.94. How many students where they?
In fact, I believe that the total payment should be $18.49. In that case, 1849 = 43^2. That gives a unique solution: 43 students, each paying 43¢. That's pretty good value for tea and a sandwich. I guess the cafeteria is subsidised after all.