The speed of a kayaker is 5.75 mi/h paddling with the river current and 3.25 mi/h paddling against it. what is the speed of the river current?

The speed of river current is 1.25 miles per hour

Solution:

Given that speed of a kayaker is 5.75 mi/h paddling with the river current and 3.25 mi/h paddling against it

To find: speed of river current

In water, the direction along the stream is called downstream

And, the direction against the stream is called upstream

Therefore, from given statement,

Speed of downstream = 5.75 miles per hour

Speed of upstream = 3.25 miles per hour

Formula to be used:

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

Speed upstream = (u - v) km/hr

Therefore, we get

5.75 miles per hour = u + v

u + v = 5.75 eqn 1

3.25 miles per hour = u - v

u - v = 3.25 eqn 2

Solve the above two equations

Add eqn 1 and eqn 2

u + v + u - v = 5.75 + 3.25

2u = 9

u = 4.5

Substitute u = 4.5 in eqn 1

4.5 + v = 5.75

v = 5.75 - 4.5

v = 1.25

Thus speed of river current is 1.25 miles per hour