半个小时用英语怎么写

　　She does an hour's piano practice every day.

　　她每天练一小时钢琴。

　　It takes me an hour to walk there and back.

　　我步行往返要花一个小时。

　　You're allowed an hour to complete the test.

　　你们有一个小时的时间来完成这次测验。

　　The performance finally started half an hour late.

　　晚了半小时以后演出终于开始了。