How do many people farm on the indo ganges plain

The Indo-Gangetic Plain, also known as the Indus-Ganga Plain and the North Indian River Plain, is a 255 million hectare fertile plain encompassing most of northern and eastern India, the eastern parts of Pakistan, and virtually all of Bangladesh. The region is named after the Indus and the Ganges, and encompasses a number of large urban areas. The plain is bound on the north by the Himalayas, which feed its numerous rivers and are the source of the fertile alluvium deposited across the region by the two river systems. The southern edge of the plain is marked by the Chota Nagpur Plateau. in conclusion to this on the west rises the Iranian Plateau. 

Exposed great deposits of coal and iron ore