to calculate the imperical formula we need to follow the following steps 1)find the % of each element in the compound 2)divide the % with the atomic mass of the element to get the simplest ratio 3)divide the simplest ratio with the least simplest ratio obtained in step (2) 4)you get the empirecal formula. Analysis of the above problem: compound % simplest ratio ratio of simplest ratio Carbon (24/60) X 100=40 40/12=3.33 3.33/3.33=1 hydrogen (4/60) X 100=6.66 6.66/1=6.66 6.66/3.33=2 Oxygen (32/60) X 100=53.33 53.33/16=3.33 3.33/3.33=1 Hence the empirical formula for the above compound is CH2O ie. option (4)