The operation has a fifty-fifty chance of success.

这次手术成功的可能性是50%。

《牛津词典》

She has a fifty-fifty chance of winning.

她获胜的可能性是百分之五十。

youdao

There is still a fifty-fifty chance to win the game.

赢得这场比赛有一半的可能性。

youdao

There was less than a fifty percent chance of success.

VOA: special.2009.06.24

If the average age of death was something like forty-five, maybe a fifty-fifty chance of--high risk-- of one of the parents dying.

那么这个概率其实很低,不是吗,大概有高达50%的可能性,双亲中的一人会死去

耶鲁公开课 - 金融市场课程节选

We did everything that could be done, and toward morning we were giving them a fifty-fifty chance, maybe less than that, maybe thirty-seventy for the wife.

NEWYORKER: Beginners

But, if there was zero chance of getting caught, fifty-eight per cent said that they would break the law.

NEWYORKER: A Dirty Business

Sussex managed to prevent a boundary being scored in the final four overs, but a rasping Hughes swipe was dropped by Joyce at mid-wicket and Henriques reached fifty in the final over when Chawla spilled a difficult chance in the deep.

BBC: Sussex well beaten in first game