关于新概念英语第三册15课题目：fifty pence worth of trouble

关于新概念英语第三册15课题目：fifty pence worth of trouble
新概念英语第三册15课的题目是——
fifty pence worth of trouble
于是我查了牛津高阶
得到以下解释——
ten dollars', ￡40, etc. ~ of sth an amount of sth that has the value mentioned:
例句1 The winner will receive ten pounds' worth of books.
例句2 a dollar's worth of change

我能看得懂解释,可是解释上的例句都有's
可是这个题目没有 ,比较一下——
The winner will receive ten pounds' worth of books. ————>
ten pounds' worth of books
fifty pence worth of trouble
我糊涂了,抓狂~~
请教大师