The speed of stream is 3 km/hr
Solution:
Given that girl is swimming downstream
To find: Speed of stream
In still water she can swim at 2km/h and the river is flowing with her
Speed in still water = 2 km/hr
She covered a distance of 12km in 2h 24 min
Distance = 12 km
time taken = 2h 24 min = [tex]2 + \frac{24}{60} = 2.4 hours[/tex]
Therefore,
[tex]speed = \frac{distance}{time}[/tex]
[tex]speed downstream = \frac{12}{2.4} = 5 \text{ kilometer per hour }[/tex]
If the speed of a boat in still water is u km/hr and the speed of the stream is v km/hr, then:
Speed downstream = (u + v) km/hr
5 km/hr = 2 km/hr + v
v = 5 - 2
v = 3 km\hr
Thus speed of stream is 3 km/hr
