The direct path across the stream and perpendicular to both sides of the stream is one leg of a right triangle. The 20 meter distance on the arriving side of the stream is another leg of the right triangle. The path he actually took is the hypotenuse of the right triangle.
leg 1 = 99 m
leg 2 = 20 m
hypotenuse = ?
We have a right triangle, and we know the lengths of the two legs. We need to find the length of the hypotenuse, so we can use the Pythagorean theorem.
