errs again:

Here's a simple example. Let's take a 120W bulb connected to 120V,
which will draw 1 amp. So it uses 120Watts. To reduce the power at
the light to 50%, 60Watts, means the current would have to decrease
from 1 amp to .71amps. P=I**R That requires inserting a resistor of
49ohms in series.

Wrong. Where did you dream that up? :-) The lower temp filament
has a lower resistance. What does P=I**R mean? :-)

Inserting that, gives a total resistance of 169 amps...

And a voltage of 31 ohms? :-)

Nick