Simple (?) EE Question

[Christopher_List at Sonymusic.Com]

Hi Guys -

OK, so this is kind of a lame question - but I'm having a bit of trouble
figuring it out. I wouldn't be surprised if many of you who took EE classes
in college didn't see this question on an exam at one time or another.....

Say you got a voltage divider, connected to V1, and Ground, R1 on top, R3
on bottom.

The voltage at the divider point is V1 * (R3/(R1+R3)). Fine.

Now suppose you connect another resistor, R2, to the middle of the divider
and connect it to voltage V2?
What's the voltage at the divider point?

More generally, if you have a star of resistors R1....Rn connected to
voltages V1....Vn, is there a general formula for the voltage at the middle
of the star?

- Thanks,
CList