倍数表达法有三种：
倍数＋原级
倍数＋比较级
倍数＋名词短语
1. three times as long as
2. three times longer than
3. three times the length of
再如：和---四倍一样宽
1. four times as wide as
2. three times wider than
3. three times the width of
