This paper describes a classroom demonstration that showcases how pre-existing beliefs (e.g., stereotypes) influence problem-solving. Across four studies, participants solved riddles with gender stereotype-consistent (e.g. doctor is male) or gender stereotype-inconsistent (e.g., doctor is female; barber is female) solutions. Solve time, perceived difficulty, and perceptions of the demonstration and how it influenced learning were measured. Studies 3 and 4 extended Studies 1 and 2 by measuring objective learning through a quiz on gender stereotypes and bias. Results indicate that students solved the stereotype-inconsistent riddles slower than stereotype-consistent riddles. Stereotype-inconsistent riddles were rated as more difficult to solve than stereotype-consistent riddles. Subjectively, participants perceived the demonstration to be an effective tool, enhancing their knowledge about gender stereotypes. Objectively, participants performed better on the quiz when they solved stereotype-inconsistent riddles than stereotype-consistent riddles. These findings suggest that using stereotype-inconsistent riddles in class can help understanding about gender stereotypes and bias.