Statistics in circuits I have a circuit, in order for it to work the electricity has to travel from point $A$ to point $B$, but on its way there it encounters $4$ independent switches. If any one of them is closed the system will function properly. the probability of a switch being closed is $.3$ for all $4$ switches, what is the overall probability that the system functions. 
Currently I tried using a tree diagram but that offered me no help and quickly just made it more confusing. im not sure where to even begin or what to start with

For problems like this, solve the probability that the system will fail.  Then subtract that number from 1 to get the probability it will not fail.
For it to fail, all switches would have to fail.  That probability would be $${0.7}^4$$
Subtract that from 1 to get your answer.
Your tree diagram would also work.  It would need to be 4 tiers.  You would find that all paths work except for the path where all 4 switches failed.  The sum of the 15 other paths is found the same way I detailed above.
