Question 1157574


speed of 60 mph on land  let distance be x  
and then use a motorboat that travels at a speed of 20 mph in still water.
against current speed = 20-4=16 mph. River distance be y

Time forward journey 
x/60 +y/16 = 4.5

Time return motorboat
speed = 20+4 =24 (with current)
x/60+y/24 =3.5


x/60 +y/16 = 4.5
60y+16x= 60*16*4.5


x/60+y/24 =3.5

60y+24x = 60*24*3.5

16.00	x	+	60.00	y	=	4320.00			
									
									
24.00	x	+	60.00	y	=	5040.00	.............2		
Eliminate 	y								
multiply (1)by		-1.00							
Multiply (2) by		1.00							
-16.00	x		-60.00	y	=	-4320.00			
24.00	x		60.00	y	=	5040.00			
Add the two equations									
8.00	x				=	720.00			
/	8.00								
x	=	90.00							
plug value of			x	in (1)					
16.00	x	+	60.00	y	=	4320.00			
1440.00		+	60.00	y	=	4320.00			
			60.00	y	=	2880.00			
				y	=	48.00			
Ans	x	=	90.00						
	y	=	48.00