It uses logic as a way to connect similar values eg. 1cc (cubic centimeter) is equal to 1 gram of water.  1 square km = 10,000,000,000 square cm. And 0.0 degrees Celsius is the temperature at which water freezes, and 100 degrees Celsius at sea level is the temperature at which water boils, knowing that you can common sense the temperature space and volume.
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I think you calculating all values through