What is the sq. root of 0.09?

This is pretty much asking "what squared it 0.09". The answer is 0.3, as 0.3 to the power of 2 is 0.09

√0.09 is 0.3.

9 squared is easily 3, since 3 * 3 is 9. So since the digit 9 is in the decimal, and there is nothing besides, that would lead you to believe that 0.09 squared is something similar to 3. And once the work is done, you would end up with 0.3. (Try a calculator for proof.)