Reflection and Mirrors - Mission RM10 Detailed Help

Ima Vain is using a convex mirror with a focal length of -49.1 cm in order to apply her hourly makeup. Ima's eyebrow is a distance of 30.0 cm from the mirror surface. What is the corresponding image distance (in cm)?


 
The mirror equation relates the object distance (do), the image distance (di) and the focal length (f):
 
1 / do + 1 / di = 1 / f


 
The mirror equation, with its three reciprocal terms, is a little awkward to work with. It's recommended that you begin this problem by performing an algebra step to rearrange the equation such that the image distance (the unknown) is by itself on the left side of the equation. Then substitute the two numerical values into the equation and use your calculator to evaluate the right side. Once done, the reciprocal of the image distance is equal to the number on your calculator. Take the reciprocal of this number to determine the image distance.


 
The Minds On Physics program calculates answers accurate to the fourth decimal place. Your answer does not need to be that accurate. The program will allow you to have a 1 percent deviation from the right answer without being wrong. This means two things: 1) Enter your answer with at least three significant digits. 2) Do not round any numbers until your final calculation.