请教各位大虾一个GAMT数学题：Ittakes30daystofillalaboratorydishwithbacteria.Ifthesizeofthebacteriacolonydoubleseachday,howlongdidittakeforthebacteriatofillonehalfofthedish?正确答案是29days,小弟很

Question

请教各位大虾一个GAMT数学题
：It takes 30days to fill a laboratory dish with bacteria. If the size of the bacteria colony doubles each day, how long did it take for the bacteria to fill one half of the dish?
正确答案是29days,小弟很不解请大虾解释一下.谢啦
我想知道的是为什么答案是29天啊。。我总觉得是15天。。。

Answer 1

一种细菌需30天长满一个实验室"碟"(载玻片,放在显微镜下的那种东西),如果细菌每天"复制"自己一次,复制自己使"碟"一半长满这种细菌需多少天? 当然是29天(days)啦
29天复制一半,30天就刚好全部了
假设有1个细菌
0天:1,
1天:2,
2天:4
3天:8
n天:2^n(2的n次方)