system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why were black people considered 3/5 of a person? Obviously they didn't want blacks to be a "full person". But 3/5 just sounds like such an random number.
gpt
It's important to note at the beginning that the "3/5ths compromise" came up in a debate about voting.  

The Slave states wanted slaves to count as whole "people" for the purposes of voting.  This would mean they'd have more representatives and have more influence in presidential elections, because they'd be counting the slaves, who wouldn't be able to vote but would still "count."  The non-slave states didn't want slaves to count at all.

That's why three fifths was arbitrary. It wasn't mean to capture the role of the slaves in society or how much they counted for in law. It was the amount that the non-slave states could live with and the slave states could accept when it came to political representation.