A lens forms a diminished and erect image of an object. The magnification is 1 / 4. Then the ratio of object distance to focal length is

(4)Since the image is diminished and erect, the lens must be a concave lens.Now   vu=14   ⇒   v=u4∴   General  lens  formula   is   1v−1u=1f∴    1−u/4 −1−u − 1−f⇒    −3u=−1f     ⇒    uf=3