This is somewhat a homework assignment, but please bear with me. Given the following schematic, I want to know the overall resistance when measured from node A to node B.
First of all, I'm not sure whether the order of calculations is important. Here's what I did: R3 and R4 are in series, so they add up to 500 Ohm. R2 is in parallel to those two, so (1/500+1/500)^-1 = 250 Ohm. Now I add R1 and my previous result because they are in series and thus get 1250 Ohm.
Is this way of calculating correct? If I, for example, first calculate R2 and R3 in parallel, and then in series with R4, I get a completely different result, which confuses me a lot.