The "empirical formula weight" for CH2O is 30.0

1) 30.0 / 30.0 gives 1, so the molecular formula is the same as the empirical formula: CH2O

2) 60.0 / 30.0 gives 2, so the molecular formula is twice the empirical formula: C2H4O 2

2) 180.0 / 30.0 gives 6, so the molecular formula is six times the empirical formula: C6H12O 6