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题库 / Prep2007E1-PS-149
A certain library assessesfines for overdue books as follows. Onthe first day that a book is overdue, the total fine is $0.10. For each additional day that the book isoverdue, the total fine is either increased by $0.30 or doubled, whicheverresults in the lesser amount. What isthe total fine for a book on the fourth day it is overdue?
$0.60
$0.70
$0.80
$0.90
$1.00
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第1天 0.1
第2天,(1)0.1+0.3=0.4; (2)0.1*2=0.2, 第2天0.2
第3天,(1)0.2+0.3=0.5; (2)0.2*2=0.4, 第3天0.4
第4天,(1)0.4+0.3=0.7; (2)0.4*2=0.8, 第4天0.7
解释得真棒！
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原来如此，我还以为是要加上两倍，人傻了
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每天都取最小不是最后取最小值
这题理解题意是关键，每一天都按最低的方法走，画个二叉树就明白了
题目里说了，每天要么增加0.3，要么翻倍。总值要最小，0.1开始，总值最小的途径是，翻倍，翻倍，加0.3.最后得0.7，其他任何路径得到的值都大于0.7
For each additional day that the book isoverdue, the total fine is either increased by $0.30 or doubled, whicheverresults in the lesser amount.
这是每一天的标准，所以第二天0.2，第三天0.4，第四天0.7
理解题意是关键。
whicheverresults in the lesser amount
For each additional day that the book is overdue, the total fine is either increased by $0.30 or doubled, which ever 【results in the lesser amount】.
取较少的金额