Questions and Answers about the Course Content

Hi Leon,

That is not the correct way. You cannot mix volts and ohms like that in your calculations.

The total resistance is 21 Ω.

But, these are parallel resistors, so you have to use the parallel resistance formula.

You want to solve this equation:

\( \frac{1}{R_2} + \frac{1}{R_2} + \frac{1}{R_2} = \frac{1}{21} \) 

or

\( \frac{1}{78} + \frac{1}{91} + \frac{1}{R_2} = \frac{1}{21} \) 

or

\( R_2 = \frac{1}{\frac{1}{21} - \frac{1}{78} - \frac{1}{91}} \) 

Thanks
Bart