The issue is with your code. It appears you looked up the conversion factor for mpg to kpl online, but that number isn't precise enough. You should use the numbers provided in the description to solve the kata. The numbers that you see in the test results that have more decimal places than necessary is due to the fact that some floating point numbers cannot be precisely represented in binary. Your solution also generates numbers like this. You will see them if you hit the attempt button a few times with your current solution.

one on the expected answers with c has a 1 all the way in the 10thousandths place.