关於fortune词性的问题

Question

注意这个句子：
These two brothers decided to go to America to try their fortunes.
这兄弟俩决定去美国碰碰运气。

句中的FORTUNE如果解释为“运气，好运”的话，那应该是不可数名词才对呀，为什麽要加“-s”的咧？而且还给了一个固定搭配叫try one's fortune是“碰运气”的意思……
也许书上翻译有误，这里应该将它翻译为“命运”或者“时运”吗？？
…………完全乱掉了，拜托哪位好心人解答一下哦，TIA~

Answer 1

妹妹啊，其实在这种情况下啊，中文是很不可信的，所以查牛津高阶的词典是最有效的方法

在其中fortune名词词条下的解释是：
for�6�1tune /ftun; NAmE frt/ noun
1. [U] chance or luck, especially in the way it affects people’s lives: I have had the good fortune to work with some brilliant directors. By a stroke of fortune he found work almost immediately. Fortune smiled on me (= I had good luck). note at luck
2. [C] a large amount of money: He made a fortune in real estate. She inherited a share of the family fortune. A car like that costs a small fortune. You don’t have to spend a fortune to give your family tasty, healthy meals. She is hoping her US debut will be the first step on the road to fame and fortune. That ring must be worth a fortune.
3. [C, usually pl., U] the good and bad things that happen to a person, family, country, etc.: the changing fortunes of the film industry the fortunes of war a reversal of fortune(s)
4. [C] a person’s fate or future: She can tell your fortune by looking at the lines on your hand. see hostage, seek—see also soldier of fortune

这样，根据意思的话，try one's fortune中的fortune只可能是1和4的解释
看1啊，【不可数】指运气或机会，尤指影响人们生活的方式，意思呢约等于LUCK，按我理解有种泛指的意思。
4 【可数】指个人的运气、命运或前途，（你可能要讲，用FATE不是命运的意思么，其实它也有运气的意思，这个用法不比用作命运少，牛津双解里还有destiny这个解释，可能改版的时候觉得和fate的意思重复，删了，destiny也是命运和运气的意思）

try one's fortune它在英语中不是个原始的固定搭配，是后来的一个搭配形式，在这个句子中有特指的意思吧，我觉着释义4就是特指，所以它就是可数了。
不过还有个句子They are going to try their fortune once more.他们想再碰一次运气，这里就不可数，这个用的就是1的释义吧。

O(∩_∩)O~当然这是我个人之见啊，你琢磨看看哦

Answer 2

try one's fortune的确是碰运气之说.
我的理解是兄弟俩个碰运气自然不能说try his fortune,各有各的运气,所以为try their fortunes.