年金現金流公式含義

2014-07-21 10:47 pm
年金現金流公式
= C x ((1-PV factor) / r)
= C x ((1-[1/(1+r)^t] / r)

C = 年金 r= interest rate
不過,我不知道公式的含義,以及如何來
我不想只記住它

Please help

回答 (1)

2014-07-21 10:56 pm
✔ 最佳答案
Please read:


圖片參考:https://s.yimg.com/rk/HA00430218/o/167123865.png


2014-07-22 16:28:38 補充:
First Step:

Consider the valuation ”at time 0” for:

"C at time 1" → C/(1 + r)
"C at time 2" → C/(1 + r)²
"C at time 3" → C/(1 + r)³
 .
 .
 .
"C at time t" → C/(1 + r)^t

Then, summing all these values gives the present value of the annuity at time 0.

2014-07-22 16:29:07 補充:
Second Step:

Not "infinite" sum of geometric series.

This is just "finite" sum (有限項之和) of geometric series.
The number of terms is t in this case.

Sum of n consecutive terms in a geometric sequence:

a + ar + ... + ar^(n-1) = a(1 - r^n)/(1 - r)

2014-07-22 17:21:16 補充:
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令 S 為等比數列 n 項之和,其中 首項 = a,公比 = r

S = a + ar + ar² + ar³ + ... + arⁿ⁻² + arⁿ⁻¹   (共 n 項)
rS =   ar + ar² + ar³ + ... + arⁿ⁻² + arⁿ⁻¹ + arⁿ

兩式相減:
S - rS = a - arⁿ
(1 - r)S = a(1 - rⁿ)
S = a(1 - rⁿ)/(1 - r)

2014-07-23 15:10:12 補充:
你可否說明一下你不明白的部分?

其實以上的是該公式的證明。

等比級數有限項和無限項之和是你高中時學過的,所以現在只是一個直接應用。

如果你可以準確地指出你不明白的部分,那才可以跟進解釋。


收錄日期: 2021-04-15 16:12:00
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