What allowed the slave states to count their slaves as part of the population when paying taxes and electrified representatives

The Three-Fifths Compromise was a compromise reached among state delegates during the 1787 United States Constitutional Convention. Whether and, if so, how slaves would be counted when determining a state's total population for legislative representation and taxing purposes was important, as this population number would then be used to determine the number of seats that the state would have in the United States House of Representatives for the next ten years.

Getting elected because not many people were voting