Two Ants A-Crawling
Two ants are 100 paces apart, crawling back and forth along the same path. The first goes 1/3 pace forward a day and returns 1/4 pace, the other goes forward 1/5 pace and returns 1/6 pace. How many days before the first ant overtakes the second?
Source: Fibonacci’s Liber Abaci, 1202