With empirical formulas you are trying to find a ratio (in whole numbers) of element to element. In this case the original C:H found is 1:2.243 and 2.243 isn't very close to a whole number. By trial and error (multiply 2.243 by 2, then 3, then 4, etc...) we can find what number to multiply both sides of the ratio by - in this case 4 gives us 4:8.972 and 8.972 is pretty close to 9 (a whole number). So now we know that C:H = 4:9 (approximately)