Question

A boat is sent across a river with a velocity of 8 km/hr. If the resultant velocity of boat is 10 km/hr, then velocity of the river is :

• A. 10 km/hr
• B. 8 km/hr
• C. 6 km/hr
• D. 4 km/hr

Answer 1

Answer: (C)

6 km/hr

Answer 2

Given $\overset{\rightarrow}{AB} =$Velocity of boat= 8 km/hr

$\overset{\rightarrow}{AC} =$Resultant velocity of boat = 10 km/hr

$\overset{\rightarrow}{BC} =$Velocity of river$= \sqrt{AC^{2} - AB^{2}} = \sqrt{(10)^{2} - (8)^{2}} = 6\mspace{6mu} km/hr$