Working alone, ryan can dig a 10 ft. By 10 ft. Hole in five hours. Castel can dig the same hole in six hours. How long would it take them if they worked together?

This hole has an area of 100 ft².

This means Ryan does 20 ft² per hour

This also mean Castel does 16 2/3 ft² per hour.

20x + (16 2/3) x = 100

(36 2/3) x = 100

x = 30/11 hours (2.727272727272)