Speed of boat in still water is 12 km/h and speed of stream is 4 km/h. The boat takes total 6 hours to go and come back

Speed of boat in still water is 12 km/h and speed of stream is 4 km/h. The boat takes total 6 hours to go and come back, Find the length of river.

(a)          23 km

(b)          45 km

(c)           32 km

(d)          54 km

Sol: