multiply periodic function

例句：

1. 1. Thecost of the new car is more thanI can afford to pay.
   这辆新车的价格超出了我能够支付的。
2. 2. If youdouble the amount of money you have,you will have twice as much.
   如果你将你拥有的钱翻倍，你就会有两倍那么多。
3. 3. The population of the city hasincreased significantly over the past decade.
   过去十年里，这个城市的人口显著增加了。