Final answer:
About 75% of Russia's population is located in the geographic core region of the country, which is the Russian Plain, including the Moscow region, and extending west of the Ural Mountains.
Step-by-step explanation:
The physiographic region of Russia that contains roughly 75% of the country's population is known as Russia's geographic core, which encompasses the Russian Plain, also referred to as the Eastern European Plain or the Western Russian Plain.
This region extends west of the Ural Mountains and includes the Moscow region, the Volga region, and the Ural Mountain region. Moscow, the capital city, is a significant population center within this core area, with over 13 million people in its metropolitan vicinity. This region is known for its agricultural productivity and is a hub for both population and industry in the country.
The Ural Mountains, which mark the eastern edge of the Russian Plain, serve as the traditional dividing line between Europe and Asia and are a source of various natural resources such as coal and precious stones.
Despite the regional diversity of ethnic groups in Russia and the richness of natural resources in other areas like Siberia and the Caucasus, the majority of the population remains concentrated in the western parts near Moscow and the Russian Plain.