想问下 ，三个方差的值 和 这个计算公式是哪来的啊？

问题如下：

If the annualized volatility on the S&P 500 is 20%, what is the volatility over one day, one week, and one month?

选项：

解释：

The scale factors for the variance are 252, 52, and 12, respectively.

The volatility scales with the square root of the scale factor, and so

$20\%/\sqrt {252}=1.26\%$

$20\%/\sqrt {52}=2.77\%$

and

$20\%/\sqrt {12}=5.77\%$