So here is the problem:

A canoe has a velocity of 0.550 m/s southeast relative to the earth. The canoe is on a river that is flowing 0.550 m/s east relative to the earth.

a) Find the magnitude of the velocity of the canoe relative to the river.

b) Find the direction of the velocity of the canoe relative to the river.

Ok so here is what I understand: Since the canoe is moving at .55 m/s southeast relative to the earth, it must mean that the canoe is moving southwest relative to the river.

The part where I am stuck on is how to calculate the magnitude from the info given.