How many positive integers $n$ satisfy $\lfloor \sqrt{n} \rfloor = 5$?

For this case we have the following equation:
 root (n) = 5
 Clearing n we have:
 n = 5 ^ 2
 n = 25
 
 A positive integers n that satisfy root (n) = 5 is:
 n = 25
 (only one integer satisfies the equation given in the problem)