Question 567855
Chicago to LA plane		530	mph		09:00 AM			
LA to Chicago plane		670	mph 	10:00 AM	1hour late	
Distance   between the two		1800	miles					
Chicago to LA plane has traveled 530 miles  before LA to Chicago plane	starts
So distance between them  = 1270 when	LA to Chicago plane	starts		
Let time they take to meet be		x	hours	

add up the speeds since they are travelling towards each other				
								
Time taken to meet is same								
d=rt								
combined speed=		1200	mph					
								
1200	x	=	1270					
x=   	1.06	hours	

The first plane has traveled 1 hour extra

so the time taken for them to cross = 2.06 hours