Given: Speed of boat in still water = 12 km/h Speed of current = 3 km/h Distance covered in downstream as well as in upstream = 135 km Calculation: Speed of boat upstream = (12 - 3) = 9 kmph Speed of boat downstream = (12 + 3) = 15 kmph Time taken = (Distance travelled)/Speed Total time taken for entire journey =
135
15
+
135
9
⇒ (9 + 15) hours ⇒ 24 hours ∴ Time taken to cover the entire journey is 24 hours.