which I'm taking to be a year.

我只是将一美元持有一年
It doesn't have to be a year.

但这个时间段并不一定是一年
The interest rate has units of time,

不同时间段有不同的利率
so I have to specify a time period over which

因此我必须在不同的时间段
I'm measuring an interest rate.

细化不同的利率
Typically it's a year. If it's a one-year interest rate,

一般来说是一年如果是一年期利率
the time period is one year,

那时间长度就是一年
and the present value of $1 in one time period is given by this,

那么一美元在一年期内的现值就能这样算出
the present value of $1 in n periods

一美元在n段时期内的现值就是
is 1/(1+r)n

1除以(1+r)的n次方
and that's all there is to this.

这样就能算出来了
I want to talk about valuing streams of payments.

我想讲讲现金流量估值