SOLUTION: The brackets may have confused in the previous version of the question I submitted. This a question for solving electrical resistance in a parallel circuit. The formula is 1/Rt

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Question 200529: The brackets may have confused in the previous version of the question I submitted.
This a question for solving electrical resistance in a parallel circuit. The formula is 1/Rt = 1/R1 + 1/R2 +1/R3 + 1/Rn.
Rt represents total resistance the other fractions are separate branch resistances.
1/Rt= 1/12 + 1/15 + 1/5
Rt=?
Thank you
Found 2 solutions by solver91311, jim_thompson5910:
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!

Just add the fractions like any other fractions. Find the lowest common denominator, convert each of the three fractions, then add the numerators.





And only has the factor

So, you need two 2s, one 3, and one 5 as factors for your LCD.



So:



Therefore



Just a little less than 3.

By the way, your general formula should be represented thus:



indicating an indefinite number of terms.



John

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
1%2F%28R%5Bt%5D%29=1%2F12%2B1%2F15%2B1%2F5 Start with the given equation.


Multiply EVERY term by the LCD 60R%5Bt%5D to clear out the fractions.


60=5R%5Bt%5D%2B4R%5Bt%5D%2B12R%5Bt%5D Multiply and simplify


60=21R%5Bt%5D Combine like terms.


60%2F21=R%5Bt%5D Divide both sides by 21 to isolate R%5Bt%5D.


R%5Bt%5D=60%2F21 Rearrange the equation.


R%5Bt%5D=20%2F7 Reduce


R%5Bt%5D=2.8571 Approximate the right side


So the total resistance is approximately 2.8571 ohms (assuming that's the unit you're working with).