Answer:
4 Fe + 3 O₂ → 2 Fe₂O₃
Explanation:
Let's start with the oxygen.
Reactants - 2
Products - 3
What number do 2 and 3 have in common? 6.
Put a 3 in the reactants and a 2 in the products to balance the oxygen.
Fe + 3 O₂ → 2 Fe₂O₃
Now let's look at the iron.
Reactants - 1
Products - 4
Put a 4 in the reactants to balance the iron.
4 Fe + 3 O₂ → 2 Fe₂O₃
The equation is balanced. Hope that helps.
Without using the scientific method, it would be much harder to determine a factor that could cause your experiment to fail. By sticking to only one of the methods you could easily destroy your experiment without the background search needed or the materials planned out.