They learn at school.

A man in a dark jacket and blue jeans sits on a yellow bench between two young girls in matching white and black dresses, holding a microphone and speaking to the camera. The girls react to his questions, with one looking at her phone and the other gesturing, as on-screen text displays a question about centimeters in a meter and the answer "1000 cm". The scene is set outdoors on a bridge with wooden buildings in the background.