We can use the Pythagorean formula to find the hypotenuse of the right triangle.
a²+b²=c²
Where a and b are the legs of the triangle and c is the hypotenuse.
According to the given problem,
one leg: a= 5 feet and second leg : b = 15 feet.
So, we can plug in these values in the above equation to get the length of unknown side. Hence,
5²+15²=c²
25 + 225 = c²
250 = c²
c =√ 250
c = √(25*10)
c = √25*√10
c = 5√10
Hence, the exact length of the hypotenuse is 5√10 feet.