A cell divides into 3 identical cells after 1 hour, and the division continues for 9 hours to fill a container. How many hours are needed to make the divided cells fill one-ninth of the container.
一个细胞1小时后分裂成3个同样的细胞，如此分裂下去9个小时可以把一个容器装满，请问要使分裂的细胞能装到容器的九分之一，需要多少小时小时．
<result>7</result>