physics...........
posted by PHYSICS .
What is the probability that the bulb is glowing for a circuit set up as:
(Bulb)
 
  (Voltage) 
 
 
(Switch1)(Switch2)

probability that a switch is on = p, therefore probability that it is off = (1p)
There are four possible configurations for the switches
1. A and B off [(1p)(1p)]
2. A and B on [ p * p ]
3. A on, B off [ p (1p)]
4. B on, A off [ (1p)p }
Only #2 leads to light.
so
p*2 = p^2
if p = 1/2
then 1/4