1. The problem statement, all variables and given/known data A lens has a focal length of f=20cm. If an object is at o=50 cm, where is the image? 2. Relevant equations 1/f = 1/o + 1/i 3. The attempt at a solution 1/20 = 1/50 + 1/i 5/100 = 2/100 + 1/i 3/100 = 1/i i = 100/3 I'm not sure how the answer could be 1/20 = 1/50 + 1/(100/3)? What am I doing wrong?