Question 439419
Pipe A  	3	hours				
It does 	  1/ 3	of the job in 1 	hour			
Pipe B 	2	hours				
It does 	  1/ 2	of thejob in 1 	hour			
Together they will do   1/ 3 +  1/ 2	
Together they will do   5/ 6 of the job in one 	hour
So they will take 1 1/5	hours		
So they will take 1.2	hours	= 72 minutes