倍数的表示法
1. 表示几倍大小（长短；数量），由倍数+ the size（length, amount...）结构组成。如：
The earth is forth-nine times the size of the moon.
2. 表示比大几倍，由倍数+形容词（副词）比较级+ than +被比较部分结构组成。如：
This box is three times bigger than that one.
3. 表示是倍，由倍数+ as +形容词+ as +被比较部分结构组成。如：
Our factory is twice as big as theirs.