six and a half million为什么是650万 关键是a half 在表示数量时怎么用

1,500,000（150万） 是one and half million还是one and a half millio one and a half million 是多少?为什么 five and a half million square kilometres ,是550万还是550百万 five and a half million 怎么翻译 more than half后面是a million 还是 of million half的用法是 one and a half years 还是one and a half year?half具体的用 half a million是什么意思 a half million seventeen and a half million 是多少 a hoot and a half该怎么翻译?a...and a half是固定用法吗?该怎么用呢? 是one year and a half还是a year and a half?为什么? half a million和a half million 有什么不同