Answer: The speed of the river's current is [tex]1.1 \frac{m}{s}[/tex]
Step-by-step explanation:
Let's begin by explaining that Speed is a relation between an object's traveled distance in a given time :
[tex]s=\frac{d}{t}[/tex]
So, in this situation the man traveled a distance [tex]d=1 km=1000 m[/tex] for a time [tex]t=15 min \frac{60 s}{1 min}=900 s[/tex] before realizing he lost his hat.
Keeping this information in mind we can calculate the speed of the river's current, since we already have a reference point: the bridge where the hat fell.
[tex]s=\frac{1000 m}{900 s}[/tex]
Then:
[tex]s=1.1 \frac{m}{s}[/tex]This is the speed of the river's current