新题型prep中的数学跪求讲解~~~

无忧小乐

a certain libray assesses fines for overdue book as follow .on the first day that a book is overdue ,the total fine is $0.1
.For each additonal day that the book is overdue ,the total fine is either increased by $0.3 or doubled,which ever results in
in the lesser amount.what is the total fine for a book onthe fourth day it is overdue?
A$0.6
B$0.7
C$0.8
D$0.9
E$1.0
答案B
求讲解~~我选的c错了~~不理解的说~

fuchengxuan

很简单，你没看懂题。就是说罚金是之前翻倍或者加0.3，怎么少怎么来。0.1 0.2 0.4 0.7

无忧小乐

哦~是也~~理解错了~~我以为在三天中选了一种方式就不变了~~谢谢啊~~~