Question

A motor boat takes 2 hours to travel a distance of 9 km downstream and it takes 6 hours to travel the same distance against the current. The speed of the boat in still water and that of the current (in km/h) respectively are:

• A. 6,5
• B. 3,1.5
• C. 8,5
• D. 9,3

Answer 1

The correct option is B 3,1.5

$D_S=\frac{9}{2}=4.5km/h$
$U_S=\frac{9}{6}=1.5km/h$
$\therefore$ Speed of boat in still water $=\frac{4.5+1.5}{2}=3km/h$
and Speed of river $=\frac{4.5-1.5}{2}=1.5km/h$