$\frac{1}{31} + \frac{1}{32} + \frac{1}{33} + ... + \frac{1}{39} + \frac{1}{40} > \frac{1}{4}$;
$\frac{1}{32} > \frac{1}{40}; \frac{1}{33} > \frac{1}{40}; \frac{1}{34} > \frac{1}{40}$ и так далее.
$\frac{1}{31} + \frac{1}{32} + \frac{1}{33} + \frac{1}{34} + ... + \frac{1}{39} + \frac{1}{40} > \frac{1}{40} + \frac{1}{40} + \frac{1}{40} + ... + \frac{1}{40} + \frac{1}{40} = \frac{10}{40} = \frac{1}{4}$, верно.