1. The problem statement, all variables and given/known data How many excess electrons are on a ball with a charge of -4.00*10^-17 C? 2. Relevant equations I know that the charge per electron is 1.60 *10^-19C. 3. The attempt at a solution My textbook does not explain how to do this, but I thought I would divide-->4.00*10^-17 C * 1 electron/-1.60*10^-19. I got -2.5*10^-36. The answer from the book is 2.5*10^2 electrons. I did some messing around and did this-->4.00*10^-17C*1 e/1.60*10^19C=2.5*10^2 electrons. What's the correct way to do this problem? Thanks in advance.