Let rate upstream=x km/hr and rate downstream=y km/hr.
Then,40/x +55/y =13…(i) and 30/x +44/y =10 .....(ii)
Multiplying (ii) by 4 and (i) by 3 and subtracting ,we get:11/y=1 or y=11.
Substituting y=11 in (i), we get: x=5.
Rate in still water =1/2(11+5)kmph= 8 kmph.
Rate of current=1/2(11-5)kmph=3kmph