1] A boat running downstream covers a distance of 16 km in 2 hours while for covering the same distance upstream,it takes 4 hours.What is the speed of the boat in still water.
a] 2  b] 4  c] 6 d] 8

solution
rate downstream = (16/2) = 8 kmph
rate upstream = (16/4) = 4 kmph
speed in still water is (1/2) (8+4) = 6 kmph