Final answer:
Around age 11, children enter Piaget's formal operational stage, where they start to comprehend abstract ideas and engage in hypothetical thinking.
Step-by-step explanation:
According to Piaget, children enter into the formal operational stage around age 11. In this stage, children begin to understand abstract ideas and are capable of hypothetical thinking. This developmental phase allows for advanced problem solving, exploring alternative solutions, and testing hypotheses. It marks a shift from concrete thinking to a more sophisticated, abstract understanding of the world, enhancing cognitive abilities significantly.