Answer:
225.
Step-by-step explanation:
We have been given some numbers. We are asked to find the number, which is a square.
Let us take square root of each number one by one.
\(\sqrt{128}=11.3137084\); Not a square.
\(\sqrt{225}=\sqrt{15^2}=15\); A square.
\(\sqrt{360}=18.9736659\); Not a square.
\(\sqrt{399}=19.974984\); Not a square.
Therefore, 225 is a square.