Question 816540
boat   	speed	=x	mph					
current     	speed	=y	mph					
against  	current     	7	hours					
with	current     	4	hours					
								
Distance against 		56	miles	distance with 		56	miles	
t=d/r	against	current     		-				
56.00	/	(	x	-	y	)=	7.00	
7.00	(	x	-	y	)	=	4.00	
7.00	x	-	7.00	y	=	56.00	....................1	
								
56.00	/	(	x	+	y	)=	4.00	
4.00	(	x	+	y	)	=	56.00	
4.00	x	+	4.00	y	=	56.00	...............2	
Multiply (1) by	4.00							
Multiply (2) by	7.00							
we get								
28.00	x	+	-28.00	y	=	224.00		
28.00	x	+	28.00	y	=	392.00		
56.00	x	=	616.00					
/	56.00							
x	=	11.00	mph					
								
plug value of x in (1)				y				
7.00	x		-7.00	y	=	56.00		
77.00			-7.00	-77.00	=	56.00		
-7.00	y	=	56.00					
-7.00	y	=	-21.00	mph				
	y	=	3.00					
boat   	speed	11.00	mph					
current     	speed	3.00	mph					
								
m.ananth@hotmail.ca