Question

A boatman can go certain distance downstream in 2 hrs. and upstream same distance in 3 hrs. If the stream flow at the speed of 4 km/h, find the speed of boat in still water.

• A. 8 km/h
• B. 12 km/h
• C. 20 km/h
• D. 10 km/h

Answer 1

Answer:

C. 20 km/h

Let the speed of the boat in still water is B km/h. Since he is traveling the same distance upstream and downstream; (B + 4)×2 = (B − 4)×3 ⇒ 2B + 8 = 3B ⇒ B = 8 + 12 ⇒ B = 20 km/hr