My advice still stands. How exactly does your book portray the formula? Because it won't be like that. Take a picture if you can. Is the letter N inside the square root symbol, or outside?

It doesn't matter either way, the way you're typing it in is still ambiguous. There's no way to tell what you're actually trying to calculate. Do you want to calculate (.63*.37)/900 and then square root it, or do you want to calculate (.63*.37), square root it, and then divide it by 900? These are not the same thing and will give you different answers, and currently the calculator can't tell what you mean and is having to guess, incorrectly. You need to use brackets to distinguish which one you mean. Can you do that? Do you understand how to use brackets?