double model

例句：

1. 1.We need to double the number of workers for the project.
   我们需要为这个项目增加一倍的工人。
2. 2.The price doubled after the promotion.
   促销后价格翻倍了。
3. 3. She doubled her savings to buy a new car.
   她将储蓄加倍，买了一辆新车。