1. The problem statement, all variables and given/known data The distance between the objective and eyepiece lenses in a microscope is 21cm . The objective lens has a focal length of 5.5mm. What eyepiece focal length will give the microscope an overall angular magnification of 350? 2. Relevant equations M=(25*d)/(fe*fo) or M=(25*d)/(fe*fo)+25? where d=5.5cm, M=350, f0=21cm, and fe is unknown 3. The attempt at a solution The online program says the answer is 2.4cm using the second equation, so I'm wondering why I don't use the first equation that doesn't add +25, and where the +25 came from? It's really bugging me. (I do not mean the first 25 which is being multiplied by d).