Question 120361
yes, there is "some formula", but if you look at the problem and understand what's going on, its pretty easy


when multiple people work together on a task, each one does some fraction
__ that fraction is based on how fast a person can do the job alone
__ fraction of task=(time together)/(time alone)


think about it __ if Joe can do a job in 3 hrs, and he works in a group that takes 1 hr, Joe does 1/3 of the job


in 8 days, A does 8/12 or 2/3 of the job
__ this means it takes B 8 days to do 1/3 of the job


so how many days for B to do 3/3 (the whole thing)?