At summer camp, the swimming course runs the length (L) of a small lake. To determine the length of the course, the camp counselors measure the two "dry" legs of a right triangle. What is the length in meters of the swimming course in the figure below?

47.17 m

Explanation:

From the diagram of the question attached, The length of the legs are 25 m and 40 m . This legs form a right angle triangle with the length of the swimming course (L).

Pythagoras theorem states that for a right angle triangle with hypotenuse a and legs b and c, then:

a² = b² + c²

In the triangle, the length of the swimming course (L) is the hypotenuse and the two legs are 25 m and 40 m. Using Pythagoras:

L² = 25² + 40²

L² = 625 + 1600

L² = 2225

L = √2225

L = 47.17 m

one "light year" is the distance that light travels, through vacuum, in one julian year.   that's 365.25 days, of 24 hours each.