Question 503346
Plane I		420	m/h				
Plane II		440	m/h			
Distance   		3440	miles					
Let time they take to be 3440 miles be		x	hours					
Plane I	distance traveled	420	x	miles   				
Plane II	distance traveled	440	x	miles   				
								
Time  is same								
t=d/r								
combined speed=		860	mph					
								
860	x	=	3440					
x=   	4	hours