How Far is the Second Object from the Convex Mirror?

[lizzyann31]

Homework Statement

An object is located 14 cm in front of a convex mirror, the image being 7 cm behind the mirror. A second object, twice as tall as the first one, is placed in front of the mirror, but at a different location. The image of this second object has the same height as the other image. How far in front of the mirror is the second object located?


I know I need to use the mirror equation... but I am totally LOST!

 

[rl.bhat]

First of all find the focal length of the convex mirror and magnification. In this problem magnification v/u = 1/2 = I/o. When the When the size of the object doubles keepin image height the same. magnification becomes 1/4.
So V'/U' = 1/4. Write V' in terms of U', substitute in the mirror formula to get U'