# of equal resistance

• Feb 27th 2008, 12:35 PM
lovinhockey26
of equal resistance
What resistance must be placed in parallel with a 149 Ohm resistor to make the equivalent resistance 124 Ohm?
• Feb 27th 2008, 12:41 PM
Peritus
• Feb 27th 2008, 12:49 PM
lovinhockey26
I'm still not sure what I need to use...
I'm not really adding the resistance... I'm trying to find the resistance necessary to be placed parallel to make the equivalence resistance 124 ohm...

still confused i guess...
• Feb 27th 2008, 01:43 PM
Aryth
Well, we use the formula for parallel resistors to find the equivalent resistance for two resistors:

$\text{We have the following information: }$

$R_1 = 149 \Omega$

$R_{Total} = 124 \Omega$

$\text{The Equation is: }$

$\frac{1}{R_{Total}} = \frac{1}{R_1} + \frac{1}{R_2}$

$\frac{1}{124} = \frac{1}{149} + \frac{1}{R_2}$

$\frac{1}{124} - \frac{1}{149} = \frac{1}{R_2}$

$\frac{149}{18476} - \frac{124}{18476} = \frac{1}{R_2}$

$\frac{25}{18476} = \frac{1}{R_2}$

$R_2*\frac{25}{18476} = 1$

$25R_2 = 18476$

$R_2 = \frac{18476}{25}$

$R_2 = 739.04 \Omega$

And there you go.
• Feb 28th 2008, 10:36 AM
lovinhockey26
you have been very helpful, I appreciate your knowledge and assistance beyond what I can express..

Thank you :)