If it takes Bob 4 hours to build a table, Sue 6 hours to build a table, and Jim 12 hours to build a table, how long will it take them to build a table together, assuming they do not hinder each other in any way?
+37146 Bob rate 1 table /4hr = 1/4
Sue rate = 1/6
Jim rate = 1/12
Build 1 table 1 / (1/4 + 1/6 +1/12 ) hr = 2 hours
