3. How many four-digit natural numbers have the product of their digits equal to 24? Write them down!
3. Since $24=2 \cdot 2 \cdot 2 \cdot 3$, the corresponding quadruples of digits are:
a) $2,2,2,3$,
b) $1,2,3,4$,
c) $1,2,2,6$,
d) $1,1,3,8$,
e) $1,1,4,6$

The required numbers are:

$\begin{array}{lr}\text { a) } 2223,2232,2322,3222, & 1 \text { point } \\ \text { b) } 1234,1243,1324,1342,1423,1432,2134,2143,2314,2341,2413,2431,3124,3142,3214,3241, \\ 3412,3421,4123,4132,4213,4231,4312,4321, & 2 \text { points } \\ \text { c) } 1226,1262,1622,2126,2162,2216,2261,2612,2621,6122,6212,6221, & 2 \text { points } \\ \text { d) } 1138,1183,1318,1381,1813,1831,3118,3181,3811,8113,8131,8311 . & 2 \text { points } \\ \text { e)1146,1164,1416,1461,1614,1641,4116,4161,4611,6114,6141,6411. } \\ \text { There are 64 numbers with the required property. } & 2 \text { points } \\ \text {.................................................................................................................... } & 1 \text { point }\end{array}$