Make up the formulas of Oxygen compounds more (by mass fraction) in potassium permanganate or berthollet salt?

Given:
Potassium permanganate
Bertoleth’s salt

To find:
ω (O in potassium permanganate)? ω (O in Berthollet’s salt)

Decision:
1) Potassium permanganate – KMnO4;
2) Mr (KMnO4) = Ar (K) * N (K) + Ar (Mn) * N (Mn) + Ar (O) * N (O) = 39 * 1 + 55 * 1 + 16 * 4 = 158 ;
3) ω (O in KMnO4) = N (O in KMnO4) * Ar (O) * 100% / Mr (KMnO4) = 4 * 16 * 100% / 158 = 40.51%;
4) Bertoleth’s salt – KClO3;
5) Mr (KClO3) = Ar (K) * N (K) + Ar (Cl) * N (Cl) + Ar (O) * N (O) = 39 * 1 + 35.5 * 1 + 16 * 3 = 122.5;
6) ω (O in KClO3) = N (O in KClO3) * Ar (O) * 100% / Mr (KClO3) = 3 * 16 * 100% / 122.5 = 39.18%;
7) ω (O in KMnO4)> ω (O in KClO3).

Answer: The mass fraction of O in KMnO4 is greater than in KClO3.