Swan陈师雯 · 2021年03月29日
NO.PZ2018062016000006
问题如下：
Lucy believes that after retirement she will need about $2 million totally for her daily expenses. At present, she has $1million investment at a stated annual interest rate of 2.5%. Assuming compounded daily, how long does it take for Lucy to have enough money for retirement life?
选项：
A.27.73 years
B.28.07 years
C.26.48 years
解释：
A is correct.
EAR=(1+0.025/365)365-1=0.02531
$1million*(1+0.02531)N =$2million, N=27.73 years.
使用后付年金的计算方法算出来是错误的结果
星星_品职助教 · 2021年03月29日
同学你好，
先付和后付年金取决于的是中间现金流（即PMT）的时间点。如果付款时间是now/today/at the beginning of the year等就是先付，如果是at the end of the year就是后付。
不取决于利率。
由于本题并没有中间现金流，PMT=0，所以不需要去考虑先付还是后付。可以试一下，两种模式下按计算器的结果必然是一样的。
计算器按键如下：
①由于选项中给的都是多少“年”，所以可以先把I/Y也转化成“年”的形式
EAR=(1+0.025/365)^365-1=0.02531，即I/Y=2.531
PV=-1，PMT=0，FV=2，I/Y=2.531，CPT N=27.7268直接得到答案A。
②也可以把期限设置成天来计算，然后再转化到年。这样的好处是可以不用去计算一个EAR
PV=-1，FV=2，PMT=0，I/Y=2.5/365=0.00685，CPT N=10,120.295（天），此处I/Y的四舍五入可能会造成结果的细微差别。
转化成年就是10,120.295/365=27.7268（年）。
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这道题如果算错了，不会是因为先付/后付的原因。可以对照以上的按键检查一下，看是否是利率输入错误等原因
CY · 2021年04月13日
请问这里PV为什么用的是-1呢？
NO.PZ2018062016000006 问题如下 Lubelieves thafter retirement she will neeabout $2 million totally for her ily expenses. present, she h$1million investment a stateannuinterest rate of 2.5%. Assuming compounily, how long es it take for Luto have enough money for retirement life? A.27.73 years B.28.07 years C.26.48 years A is correct.EAR=(1+0.025/365)365-1=0.02531$1million*(1+0.02531)N =$2million, N=27.73 years. EAR为什么是2.531，不是2.5，这里I/Y为什么需要转换
NO.PZ2018062016000006问题如下Lubelieves thafter retirement she will neeabout $2 million totally for her ily expenses. present, she h$1million investment a stateannuinterest rate of 2.5%. Assuming compounily, how long es it take for Luto have enough money for retirement life?A.27.73 yearsB.28.07 yearsC.26.48 yearsA is correct.EAR=(1+0.025/365)365-1=0.02531$1million*(1+0.02531)N =$2million, N=27.73 years.求问怎么用金融计算器计算～
NO.PZ2018062016000006问题如下 Lubelieves thafter retirement she will neeabout $2 million totally for her ily expenses. present, she h$1million investment a stateannuinterest rate of 2.5%. Assuming compounily, how long es it take for Luto have enough money for retirement life?A.27.73 yearsB.28.07 yearsC.26.48 yearsA is correct.EAR=(1+0.025/365)365-1=0.02531$1million*(1+0.02531)N =$2million, N=27.73 years.请问这题能用试错法计算吗，如果能的话要怎么算，谢谢
NO.PZ2018062016000006 问题如下 Lubelieves thafter retirement she will neeabout $2 million totally for her ily expenses. present, she h$1million investment a stateannuinterest rate of 2.5%. Assuming compounily, how long es it take for Luto have enough money for retirement life? A.27.73 years B.28.07 years C.26.48 years A is correct.EAR=(1+0.025/365)365-1=0.02531$1million*(1+0.02531)N =$2million, N=27.73 years. 为什么FV是-1不是1呢？
NO.PZ2018062016000006 问题如下 Lubelieves thafter retirement she will neeabout $2 million totally for her ily expenses. present, she h$1million investment a stateannuinterest rate of 2.5%. Assuming compounily, how long es it take for Luto have enough money for retirement life? A.27.73 years B.28.07 years C.26.48 years A is correct.EAR=(1+0.025/365)365-1=0.02531$1million*(1+0.02531)N =$2million, N=27.73 years. 同题目，这题我代入FV=2, PV=-1,I/Y=2.5,PMT=0，最后算出来的就是28.07，请问这个思路为什么错了呢？
