Question

A boat takes 5 hours more while going back in upstream than in downstream. If the distance between two places is 24 km and the speed of boat in still water be 5.5 km/h. What must be the speed of boat in still water so that it can row downstream, 24 km, in 4 hours?

• A. 1.5 km/h
• B. 3.5 km/h
• C. 4.5 km/h
• D. 3 km/h

Answer 1

The correct option is B 3.5 km/h

$\frac{24}{(5.5-R)}-\frac{24}{(5.5+R)}=5$
$\Rightarrow R=2.5km/h$ R $\to$ Speed of river/current
Again $(B_2+R)=\frac{24}{4}=6$
$\Rightarrow (B_2+2.5)=6\Rightarrow B_2=3.5km/h$