Turn V into pi

Are the letters R, r the same thing or different?

R is the big cylinder, r is the small cylinder inside

I believe you just want to isolate pi  on one side of the equation???....if so, we have

V=pi*R^2*H-pi*r^2*H    factor out pi on the right....and H inside the parentheses

V = pi [ H*(R^2 - r^2)]       divide both sides by [ H*(R^2 - r^2)]  

V / [ H*(R^2 - r^2)]    = pi

Thx so much!