a year and a half：一年半

例句：For a year and a half, wage restraint on a voluntary basis worked

在一年半的时间里，自愿实行的限薪措施奏效了。

one and a half years： 一年半

例句：

One and a half years has passed.

一年半时间过去了。

Traveler: about one and a half years.

旅客：大约有一年半了。

When did he start golfing? One and a half years ago.

他什么时候开始打高尔夫的？一年半以前。