You shouldn't have to think about it. When I ask a chick out it's usually a spur of the moment kind of thing, and half the time I don't even expect it.
Then again you're 11 so disregard that. But go for it champ, if she rejects you then oh well, I can promise nothing bad will come of it so don't tell yourself it's the end of the world. And to everyone saying he's too young, perhaps he is, imo he should probably be trying to make friends with all of the chicks he knows rather then asking out one or two, but who gives a forget. Just be prepared to be exposed to the inexcusably handicapped mind of a pre-teen girl.