First you have to assume that 100 grams of the compound is present(70.4 grams carbon,29.6 gram hydrogen). Next,you have to divide the two by their relative molecular masses(70.4/12 and 29.4/1) That leaves 5.8666666....... and 29.4. Now divide the two of them by 5.8666666...(use exact value),which will give you 1 and 5(rounded off). Therefore,the answer is CH5.
