Question 29936
In this problem, it is neccessary to focus on the numbers you have been given, since each floor is the same height. 
Look at the proportions between 3 and 12. By simplifying this proportion, you obtain 1 to 4. (divide by lowest common multiple) 
This 1 to 4 Ratio means that it would take 4 times as long to reach the 12th floor than it would the 3rd. So look at the question your problem is asking you, if a trip to the 12th floor is 4 times longer than a trip to the third, reverse the number. This gives us 1/4. So, a trip to the 3rd floor takes 1/4 the time as a trip to the 12th floor. 
I hope this helped you and answered your question. 
-Cain