I'm having trouble find the total resistance of circuits with cells in parallel. The answer in the book is 31 ohms, but my calcuation ends up as 30 ohms. What am I doing wrong? (Please show steps if not too much trouble) Thanks in advance!:D See this site for my work and a diagram of the circuit. http://img72.photobucket.com/albums/v219/fr0st_lizard/Physics_Problem.gif The blurry thing says 2 volts/cell Internal resistance: 1 ohm/cell And the resistors in the bottom left corner are 10, 5, and 15 ohms. Sorry for my crappy drawing, I did it on paint!