Long division method is the fastest one in this case.

812/1.16 = 81200 / 116

Long division is a very common method. Take a look at prep guide (

http://www.800score.com/gmat-guide.html) if you need to go over it.

Another way is to divide each answer choice by 1.1 and multiply the result by 1.16. If you get $812, then it is the right one. If you see right away that 770 is divisible by 11, then you should start from this one and get the answer really fast.