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: