a man can swim in still water at 6 km / h , but takes twice as long to swim upstream than downstream . the speed of the stream is ?
"m = 6 s = x ds = 6 + x us = 6 - x 6 + x = ( 6 - x ) 2 6 + x = 12 - 2 x 3 x = 6 x = 2 answer : d"
divide(6, const_3)