Final answer:
The concrete-operational stage occurs during the ages of 7 to 11 years old. In this stage, children can think logically about real events, understand mathematical operations, and grasp the concept of conservation.
Step-by-step explanation:
The concrete-operational stage occurs during the ages of 7 to 11 years old. This is the third stage in Piaget's theory of cognitive development. During this stage, children can think logically about real events, understand mathematical operations, and grasp the concept of conservation. They can also work with concrete information and understand cause-and-effect relationships.