Resistance in a series / parallel?

[dolpho]

Homework Statement

Find the equivalent resistance between points A and B shown in the figure(Figure 1) . Consider R1= 2.2 , R2= 1.0 , R3 = 3.6 , R4= 5.0 , R5= 4.0 , and R6= 7.6 .

http://i.imgur.com/EBJmSvk.png

Homework Equations

For resistors in parallel, 1 / Req = 1/r1 + 1/r2 + 1/r3...etc
for resistors in series, Req= R1 + R2 + R3...etc

The Attempt at a Solution

So I think R3, R4 and R5 are parallel

1/3.6 + 1/5 + 1/4 = .72

and then I think we can combine R6, R1 and R2 into one since they are parallel also.

1 / 2.2 + 1/1 + 1/7.6 = 1.58

Now add up .72 and 1.58 since they are in series? = 2.3

Would appreciate any help, this is pretty confusing to me lol

 

[Saitama]

So I think R3, R4 and R5 are in a series.

Check this again.

 

[dolpho]

Check this again.

Ahhh I'm sorry I did a typo. I meant parallel

 

[Saitama]

Ahhh I'm sorry I did a typo. I meant parallel

Did you get the correct answer now?

 

[dolpho]

Did you get the correct answer now?

nope :( I'm not sure what I'm doing wrong

 

[Saitama]

So I think R3, R4 and R5 are parallel

1/3.6 + 1/5 + 1/4 = .72

0.72 is reciprocal of equivalent resistance of R3, R4 and R5. The equivalent of these three resistors is in series with R6.

 

[dolpho]

0.72 is reciprocal of equivalent resistance of R3, R4 and R5. The equivalent of these three resistors is in series with R6.

Ok I was just thinking that, so its actually.

.72 = 1 / Req

Req = 1.39?

Then we add that to R6 in a series? so

1.39 + 7.6 = 8.99

Now we add R6 to R2 and R1 which are parallel.

So... 1/2.2 + 1 + 1/8.99 = 1 / Req

= 1.24 = 1 / Req -----> 1 / 1.24 = .8?

 

[Saitama]

Ok I was just thinking that, so its actually.

.72 = 1 / Req

Req = 1.39?

Then we add that to R6 in a series? so

1.39 + 7.6 = 8.99

Now we add R6 to R2 and R1 which are parallel.

So... 1/2.2 + 1 + 1/8.99 = 1 / Req

= 1.24 = 1 / Req -----> 1 / 1.24 = .8?

I haven't checked out your calculations but your steps look fine to me.

 

[dolpho]

I haven't checked out your calculations but your steps look fine to me.

ARG...It's not .8...what the f...heck

 

[Saitama]

So... 1/2.2 + 1 + 1/8.99 = 1 / Req

= 1.24 = 1 / Req -----> 1 / 1.24 = .8?

Calculation mistake. 1/Req=1.56

 

[dolpho]

Calculation mistake. 1/Req=1.56

Finally! Got it right, thanks so much for your help!

 

[haruspex]

So... 1/2.2 + 1 + 1/8.99 =
= 1.24

Try that step again (btw, 8.97 is more accurate)