# Equivalent Resistance Question

by wr1015
Tags: equivalent, resistance
 P: 55 Find the equivalent resistance between points A and B for the group of resistors shown in Figure 21-29, where R1 = 93 and R2 = 40 . ok i know that $$R_{1}$$ and 35$$\Omega$$ are in series and $$R_{2}$$ is in parallel to the top 2 resistors but I am obviously making errors either in how i set up the problem or in my calculations. I have tried (1/$$R_{2}$$) + (1/2R) = 3/2R (as shown in my book) and then invert to show 2/3(R) and the answer i'm getting is wrong.. please help
 Sci Advisor HW Helper P: 1,334 You should first combine the two resistors in series, and then combine the result with the other resistor in parallel. What are the laws of combination for resistors in series? What about parallel?
P: 55
 Quote by Physics Monkey You should first combine the two resistors in series, and then combine the result with the other resistor in parallel. What are the laws of combination for resistors in series? What about parallel?
for series: $$R_{eq} = R_{1}+R_{2}+R_{3}...$$
for parallel: $$1/R_{eq}= 1/R_{1}+1/R_{2}+1/R_{3}...$$

so you're saying: 93$$\Omega$$+35$$\Omega$$+(1/40$$\Omega$$) OR (1/93 +35) + (1/40) ???

 P: 55 Equivalent Resistance Question nevermind i'm an idiot.. i was forgetting to take the inverse of the answer
 Quote by wr1015 so you're saying: 93$$\Omega$$+35$$\Omega$$+(1/40$$\Omega$$) OR (1/93 +35) + (1/40) ???