1、倍数的表达方法：(倍数+ 比较级/ as…as…/ the + n. + of…)
Our school is 【twice bigger than】 theirs.
Our school is 【three times as big as】 theirs.
Our school is 【three times the size of】 theirs.
2、主语+谓语+倍数+as+形容词原级+as+被比较的对象.
The world's population has grown to more than six times 【as large as】 it was in 1800.