Series and Parallel

[biferi]

I know if I have say 3 Resisters in Series and I know they are
R1=20 Ohm and R2=20 then the both of them will be 400 Ohm.

But if they are in Parallel do I Divide each Resister like so
R1=20 Divided by R2=20 then the Total Resistance is 1 Ohm am I right?

Please keep it simple but tell me in your own words.
Thank you.

 

[ronsimpson]

I know if I have say 3 Resisters in Series and I know they are
R1=20 Ohm and R2=20 then the both of them will be 400 Ohm.

20+20=40

But if they are in Parallel do I Divide each Resister like so
R1=20 Divided by R2=20 then the Total Resistance is 1 Ohm am I right?

.
For only two resistors, the unreciprocated expression is reasonably simple:

So R1//R2, 20//20 is 10 ohms. "//" = parallel

(1/20)+(1/20)=0.05+.05=0.10= (1/0.1) =10