Question 315857
jack takes 5 hours
Marilyn - 4 hours
jack does 1/5 of job in 1 hour
Marilyn does 1/4 of job in 1 hour.
to gether they do 1/4 +1/5 of the job in 1 hour.
1/4 +1/5 = 9/20 of the job in 1 hour
together they will do the job in 20 /9 hours
= 2.2 hours