I am tiling my kitchen, here's my problem, I have chosen 5" tiles....?

I need to know the area of the floor in square feet but the answer needs to be as an improper fraction. I have figured and figured and figured and I have come up with 129.16625 square feet, is this correct and if so, how do I convert it into an improper fraction? Someone else tried to help and came up with 270 over 12 (270/12) as the improper fraction, are they correct?