Future value换算成present value都是按照复利算的吗

题目

Future value换算成present value都是按照复利算的吗
You are considering purchasing a new home.You will need to borrow $250,000 to purchase the home.A mortgage company offers you a 15-year fixed rate mortgage at 9% APR.If you borrow the money from this mortgage company,your monthly mortgage payment will be closest to:
题目中给的是APR(Annual percent rate,单利）为什么答案是
15 years = 180 months,converting 9% APR to monthly interest rate = 9% / 12 = 0.75% monthly.PV = 250,000,r = 0.75%,n = 180,using the annuity formula:250,000=C/0.75%(1−1/(1+0.75%)^180) => C = 2535.6
这不就是把它当成复利算了吗?

答案

题目中给的APR叫做名义APR,就是简单地把每月利息乘以12而来的,并不代表利息是按单利计算的.实际利息计算需要用复利.英美习惯把名义APR简称为APR,而把实际APR（即用复利计算的APR）称为有效APR.