A 0.14-km wide river flows with a uniform speed of 4.0 m/s toward the east. It takes 20 s for a boat to cross the river to a point directly north of its departure point on the south bank. What is the speed of the boat relative to the water

The right approach is "8.1 m/s". A further explanation is provided below.

Explanation:

According to the table,

Speed of Boat

=

Now,

⇒  

or,

⇒  

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