According to Piaget, a(n) is an organized system of mental representations used to understand the world.

Base on Piaget theory, organized system of mental representations that is needed to have the understanding of the world is Schema.

Therefore, schema is the right term.

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According to Piaget, a schema is an organized system of mental representations used to understand the world.

Explanation:

According to Jean Piaget, a schema is a mental concept that facilitates our navigation through daily life by organizing information in categories. Schemas help us make sense of our environment. However, we must keep in mind that they aren't necessarily accurate. For instance, you go into the office of a professor. After you leave, you are asked about what you saw in the office. You say there were books, even though there was not a single book in the office. Why would you say it, then? Because it is a part of our schema, our idea of offices, that there should be books in the office of a professor.