# Euclidean Algorithm and Jug Filling (VIDEO!)

Given a 3-gallon jug and a 5-gallon jug, how does one obtain exactly one gallon of water? Jug Filling problems play a key role in the foundation of number theory, in particular, in proving the Fundamental Theorem of Arithmetic (all factor trees lead to the same set of primes). Here’s a brief introduction to Euclid’s continued brilliance on the topic of numbers.