A swimmer's speed in swimming pool is 6 km/hr. He swims between two points in a river and returns back to the starting point. He took 24 minutes more to cover the distance upstream than downstream. If the speed of the stream is 4 km/hr, then the distance between two points is :

1km

$\text{Speed in still water}=6\text{ km/hr}.$

$\text{Speed of stream}=4\text{ km/hr}.$

$\text{Upstream speed}=6-4=2\text{ km/hr}.$

$\text{Downstream speed}=6+4=10\text{ km/hr}.$

$\text{Let distance between the points}=d.$

$\text{Upstream time}=\frac{d}{2}.$

$\text{Downstream time}=\frac{d}{10}.$

$\text{Given upstream takes }24\text{ minutes more}= \frac{24}{60}=0.4\text{ hr}.$

$\frac{d}{2}-\frac{d}{10}=0.4.$

$\frac{5d-d}{10}=0.4.$

$\frac{4d}{10}=0.4.$

$4d=4.$

$d=1.$

$\text{Distance between the points}=1\text{ km}.$