1. The problem statement, all variables and given/known data Mary needs to row her boat across a 100 m wide river that is flowing to the east at a speed of 1.0 m/s. Mary can row the boat with a speed of 2.0 m/s relative to the water. 2. Relevant equations pythagorean theorem: a^2+b^2=c^2 3. The attempt at a solution Ok so I know this is pretty straight forward problem. But the 100 m is throwing me off here. I draw a vector diagram and add the two component vectors: (1,0) +(0,2) ------ (1,2) Now i used pythagorean theorem to find the resultant 1^2 + 2^2 = R^2, in which R=5^1/2=2.2. So she's moving accross the river at a rate of 2.2 m/s. Now I'm not sure how 2.2 m/s and 100 m finds her displacement. Any tips?