Bloody Word Problems!

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InNeedOfHelp!

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Feb 5, 2006
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I didn't find how to formulate this exactly on Karl's formula sheet, probably cause I don't know what its called, but I did the best I could.

Given the formula 1/R(little t on bottom right of R) = 1/R (little 1) + (1/R (little 2) + R (little 3) for the resistance of a circuit, determine the resistance R (little 2) if R (little 1) = 5 ohms, R (little T) =2 ohms and R (little 3) = 3 ohms.


I realize this format might be confusing.... but if anyone could help, I'd really appreciate it!
 
InNeedOfHelp! said:
I didn't find how to formulate this exactly on Karl's formula sheet, probably cause I don't know what its called, but I did the best I could.

Given the formula 1/R(little t on bottom right of R) = 1/R (little 1) + (1/R (little 2) + R (little 3) for the resistance of a circuit, determine the resistance R (little 2) if R (little 1) = 5 ohms, R (little T) =2 ohms and R (little 3) = 3 ohms.


I realize this format might be confusing.... but if anyone could help, I'd really appreciate it!
Click to expand...
\(\displaystyle \mbox{ \frac{1}{R_T} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3}}\)

We are told \(\displaystyle \mbox{R_T = 2; R_1 = 5; R_3 = 3}\) so substitute them into the equation:

\(\displaystyle \mbox{ \frac{1}{2} = \frac{1}{5} + \frac{1}{R_2} + \frac{1}{3}}\)

What we could do is multiply both sides by 30, which is the lowest common factor of 2, 5, and 3 to get:

\(\displaystyle \mbox{ 15 = 6 + \frac{30}{R_2} + 10}\)

You can solve for \(\displaystyle \mbox{\frac{30}{R_2}}\), and hence \(\displaystyle \mbox{R_2}\).
 
I'm sorry. I'm having a really off day. I have been getting so frustrated! I just don't bloody get math! Give me anything else and I'll wow you, but not math!

so if I understand this, I divide 30 by R_2? Which could be 30/2 = R? Which = 15. Is that right?
 
\(\displaystyle \mbox{ 15 = 6 + \frac{30}{R_2} + 10}\)

Simplify

\(\displaystyle \mbox{ 15 = 16 + \frac{30}{R_2}}\)

Subtract 16 from both sides

\(\displaystyle \mbox{ -1 = \frac{30}{R_2}}\)

Multiply both sides by \(\displaystyle \mbox{R_2}\)

\(\displaystyle \mbox{ -R_2 = 30}\)

Divide both sides by -1

\(\displaystyle \mbox{ \fbox{R_2 = -30}}\)
 
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