How do we spot the perfect squares among $10,100,1000,10000$ and so on?

Is one lakh a perfect square?

Find out the squares of $20, 200$ and $2000$.

Is $400000000$ a perfect square? What if we put in one more zero?

Find the square of $30$.

Find the square of $400$.

Find the square of $7000$.

Find the square of $6\times {10}^{25}$.

Check whether $2500$ is perfect square.