In this problem, you are asked to find the resultant displacement of your boat, which involves using the Pythagorean theorem. The boat moves across a river that is 35.0 m wide and is carried downstream by the river current, moving a total of 45.0 m along the river. The displacement can be visualized as the hypotenuse of a right triangle, with the width of the river as one leg and the distance moved downstream as the other leg.

The width of the river is $35.0 \, \text{m}$ and the distance moved downstream due to the current is $45.0 \, \text{m}$. The resultant displacement $d$ (the hypotenuse) is given by:

$d = \sqrt{(35.0)^2 + (45.0)^2}$

Let's calculate this.