A boat rows a distance of 12 km downstream at 13 km/h and covers the same distance upstream at 7 km/h. What is the average speed of the boat ?
Answer & explanation
Correct answer: option 2
The correct answer is option (2) : 9.1 km/h
$u= 13\, km/h$
$v= 7\, km/h$
Speed of boat in still water $x=\frac{13+7}{2}$
$= 10\, km/h$
Average speed $=\frac{u+v}{\text{Speed in still water }}$
$= \frac{13×7}{10}= 9.1\, km/h$