Question 28411

Franklin can do a job in 6 h
HENCE FRANKLIN CAN DO IN 1 HOUR .......1/6 JOB
 and Mike can do it in 4 h.
HENCE MIKE CAN DO IN 1 HOUR...........1/4 JOB  
HENCE TOGETHER THEY CAN DO IN 1 HOUR ....1/6 + 1/4 = (2+3)/12=5/12 JOB

 What part of the job can they do by working together for 2 h? 
HENCE IN 2 HOURS THEY CAN DO TOGETHER........2*5/12=5/6 JOB... 
for y h?

HENCE IN Y HOURS THEY CAN DO TOGETHER........Y*5/12=5Y/6 JOB...