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## Homework Statement

A swimmer is training in a river. The current flows at 1.33 metres per second and the swimmer's speed is 2.86 metres per second relative to the water. What is the swimmer's speed relative to the shore when swimming upstream? What about downstream?

## Homework Equations

Pythagoras.

## The Attempt at a Solution

Here's my problem. Because we're looking at vectors, I would normally do the vector sum of both the velocities and use Pythagoras, as both given vectors are perpendicular.

V

_{current}= 1.33 m/s

V

_{swimmer relative to water}= 2.86 m/s

So the resultant vector would be: [itex]\sqrt{}[/itex](1.33

^{2}+ 2.86

^{2})

Giving 3.15 m/s, however this is wrong, as the answer given is 1.53 m/s upstream.

I'm puzzled as to how this answer was reached.