Question 822919
Boat speed	=	10	km/h										
current speed	=	x	km/h										
													
speed against	current	10	-	x									
speed with	current	10	+	x									
													
Distance against	current	2	miles										
Distance with	current	4	miles										
													
t=d/r	time against = time with		current	-									
2	/	(	10	-	x	)=	4	/	(	10	+	x	)
2	(	10	+	x 	)=	4	(	10	-x	)			
20	+	2	x	=	40	-	-4	x					
4	x	2	x		40	+	-20						
6	x	=	20										
/	6												
x	=	3.33	km/h	current	speed