[LHM]

Magnetite, which has the formula Fe₃O₄, is comprised of iron(II) oxide and iron(III) oxide. What is the ratio of iron(II) ions to iron(III) ions in magnetite?

The answer is 1:2, but I fail to see how that's the answer. Isn't Fe₃O₄ also known as Fe₂O₃*FeO? so I figured that the ratio must be 1:1, but it's not. Where's the flaw in my logic?

[Schrödinger]

Isn't Fe₃O₄ also known as Fe₂O₃*FeO?

Yes it is.
One molecule of Fe₂O₃ has 2 Fe(III) atoms and one molecule of FeO has one Fe(II) atom.

That's why the ratio is 1:2

[Borek]

Where's the flaw in my logic?

You solved different question. It doesn't ask about oxide:oxide ratio, but Fe(II):Fe(III) ratio.