How many people would be there if only 3 person per acre lives on earths land

12 268 800 000

Explanation:

Landmass in total covers the area of around 57,510,000 square miles.As one square mile covers 640 it means that the whole world covers the area of around 57,510,000 * 640 - 36 806 400 000 acres.So, if only 3 people per acre would live on earth than there would be 12 268 800 000 people in total (36 806 400 000 divided with 3).

Answer they are produced by collision of tectonic plates;