问题如下图：老师你好，N=10,PV=1000,PTM=-40,FV=-900,为什么计算器算出来I/Y是3.13？再乘以2乘以0.62，就没这个答案了
选项：
A. 
B. 
C. 
解释：
粉红豹 · 2018年10月23日
萌宝宝，恰好看到你的提问。
你的算法中有个小问题哎：
1）这道题中PV= - 900，FV = 1000，而不是你说的相反哟。
注：负号代表现金流的流出，没有其他含义。
2）为了养成良好的做题习惯，PMT我们用正数
如果我们把PV定义成现金流的流入，即花了900的现金流出的代价在起初买了这个债券，那么后面收到的coupon和最终的本金收回对于我们投资者来说就是现金流的流入哟，所以PMT 和FV都是正数。
因此FV=1000, PMT=40, PV=-900, N=10, CALCULATE 1/Y= 5.319.
5.319%是半年的利率，因此乘以2就是年化的，即10.62%
题目求after-tax cost，因此就用用rd再乘以（1-t），就是10.62%*(1-38%)=6.59%
选C。
粉红豹 · 2018年10月23日
打字打错了，PV定义成现金流的“流出” 哈~~ 未来收到coupon 和 本金归还就是现金流的“流入 ”
大蒙 · 2018年10月23日
哈哈，你这么一说我发现是我又粗心搞错了。。PV和FV的值搞反了。另外关于正负号，我之前的理解是：因为公司issue了一个债券，相当于是融资，所以现金流流入900元，之后每期支付payment40以及最后支付本金1000，所以后面两笔都是流出，不知道这样理解可以不？
粉红豹 · 2018年10月23日
要从“投资者”的角度来理解做题会更顺一点哟～～～ 投资者把债券当一种理财工具，想要获得定期现金流coupon和capital gain，所以就是一开始买债券是自己的现金流出，收到coupon和最后本金归还是现金流入～
NO.PZ2016021705000022 问题如下 t.Com hterminethit coulissue $1,000 favalue bon with 8 percent coupon paisemi-annually ana five-yematurity $900 per bon If t.Com’s margintrate is 38 percent, its after-tcost of is closest to: A.6.2 percent. B.6.4 percent. C.6.6 percent. is correct.FV = $1,000; PMT = $40; N = 10; PV = -$900Solve for i. The six-month yiel i, is 5.3149%YTM = 5.3149% × 2 = 10.62985% r (1−t) = 10.62985%(1−0.38) = 6.5905% r1 − t) = 10.62985%(1 − 0.38) = 6.5905% 为啥PV=900而不是1000
NO.PZ2016021705000022问题如下t.Com hterminethit coulissue $1,000 favalue bon with 8 percent coupon paisemi-annually ana five-yematurity $900 per bon If t.Com’s margintrate is 38 percent, its after-tcost of is closest to: A.6.2 percent.B.6.4 percent.C.6.6 percent. is correct.FV = $1,000; PMT = $40; N = 10; PV = -$900Solve for i. The six-month yiel i, is 5.3149%YTM = 5.3149% × 2 = 10.62985% r (1−t) = 10.62985%(1−0.38) = 6.5905% r1 − t) = 10.62985%(1 − 0.38) = 6.5905% 给出的coupon rate都是年化的吗
NO.PZ2016021705000022问题如下t.Com hterminethit coulissue $1,000 favalue bon with 8 percent coupon paisemi-annually ana five-yematurity $900 per bon If t.Com’s margintrate is 38 percent, its after-tcost of is closest to: A.6.2 percent.B.6.4 percent.C.6.6 percent. is correct.FV = $1,000; PMT = $40; N = 10; PV = -$900Solve for i. The six-month yiel i, is 5.3149%YTM = 5.3149% × 2 = 10.62985% r (1−t) = 10.62985%(1−0.38) = 6.5905% r1 − t) = 10.62985%(1 − 0.38) = 6.5905% 为啥pv是900，老师，我感觉我前面没有学好，能详细解答吗。感谢
NO.PZ2016021705000022 问题如下 t.Com hterminethit coulissue $1,000 favalue bon with 8 percent coupon paisemi-annually ana five-yematurity $900 per bon If t.Com’s margintrate is 38 percent, its after-tcost of is closest to: A.6.2 percent. B.6.4 percent. C.6.6 percent. is correct.FV = $1,000; PMT = $40; N = 10; PV = -$900Solve for i. The six-month yiel i, is 5.3149%YTM = 5.3149% × 2 = 10.62985% r (1−t) = 10.62985%(1−0.38) = 6.5905% r1 − t) = 10.62985%(1 − 0.38) = 6.5905% 这个是C以900元的价格发行到期日为1000的债券不是，所以当期获得900的现金流入，到期付出1000.
NO.PZ2016021705000022 问题如下 t.Com hterminethit coulissue $1,000 favalue bon with 8 percent coupon paisemi-annually ana five-yematurity $900 per bon If t.Com’s margintrate is 38 percent, its after-tcost of is closest to: A.6.2 percent. B.6.4 percent. C.6.6 percent. is correct.FV = $1,000; PMT = $40; N = 10; PV = -$900Solve for i. The six-month yiel i, is 5.3149%YTM = 5.3149% × 2 = 10.62985% r (1−t) = 10.62985%(1−0.38) = 6.5905% r1 − t) = 10.62985%(1 − 0.38) = 6.5905% RT