So I bought a magnifying glass for a project and I need to find out the focal length of it in order to use it. I'm given the magnification of the converging lens, which is 5, but I don't any methods or how I could find out the focal length given only the magnification. I attempted to set distance object that I actually measured and put it into the magnification formula and then took the distance of the image and put it into the focal length formula. However, when I tested it out it didn't seem quite right. Are there anyways I could do this mathematically? If not how else could I do this?