How to slove 1800=16Var[X]-120Var[X}^1/2?Ask Variance[X]
This is the question from Schweser old exam practice.Thank you..

Hi Gladys

It’s a quadratic, so let y = standard deviation of x. Then

16y^2 - 120y - 1800 = 0, and
(4y+30)(4y-60)=0, so
y = {15,-7.5}
Var(x) = {225,56.25}

(this is a bit unusual for FRM, you are not likely to see this sort of thing in FRM 2008)

Thanks, David

Hi David,

I am attachin an image that has a question in it.Answer is A

Thanks
Sipani

Hi Sipani, no attachment? David