If there is a fifty-fifty chance of something happening, it is equally likely to happen as it is not to happen.
You’ve got a fifty-fifty chance of being right.
She has a fifty-fifty chance of winning (= an equal chance of winning or losing).
If there is a fifty-fifty chance of something happening, it is equally likely to happen as it is not to happen.
You’ve got a fifty-fifty chance of being right.
She has a fifty-fifty chance of winning (= an equal chance of winning or losing).