<PRE><B>Question 350769</B>
let the speed of boat in still water be x mph
speed of current 4 mph
..
speed upstream = x-4 mph
speed downstream = x+4

..
distance = 8 miles upstream 
time upstream = 8/x-4
..
time downstream = 16/x+4)
..
both the times are same
..
8/(x-4) = 16/(x+4)
8(x+4)=16(x-4)
8x+32=16x-64
16x-8x=64+32
8x=96
x= 12 mph speed of boat in still water </PRE>