Boat and Stream

if the speed of a boat in still water is u km/h & the speed of the streams of v km/h than-
speed towards downstream- (u+v) km/h
Speed towards up stream- (u-v) km/h
if the speed of boat in downstream u km/h and in upstream v km/h
than speed in still water-\frac{1}{2}(u+v) km/h
rate or speed of stream=\frac{1}{2}(a-b) km/h