4. Zadatak

Odgovarajuće četvorke znamenaka su:

a) $9$, $9$, $9$, $5$,

b) $9$, $9$, $8$, $6$,

c) $9$, $9$, $7$, $7$,

d) $9$, $8$, $8$, $7$,

e) $8$, $8$, $8$, $8$.

S traženim svojstvima su sljedeći brojevi:

a) $9995$, $9959$, $9599$,

b) $9986$, $9968$, $9896$, $9869$, $9698$, $9689$, $8996$, $8969$, $8699$,

c) $9977$, $9797$, $9779$, $7997$, $7979$, $7799$,

d) $9887$, $9878$, $9788$, $8987$, $8978$, $8897$, $8879$, $8798$, $8789$, $7988$, $7898$, $7889$,

e) $8888$.

Traženih brojeva ima ukupno $31$.