Use the digits without repetition and make the greatest and smallest $4-$ digit numbers: $2,\ 8,\ 7,\ 4$.

Given: Digits: $2,\ 8,\ 7,\ 4$.

To do: To make the greatest and smallest $4-$ digit numbers with the given digits.

Solution:

Given digits: $2,\ 8,\ 7,\ 4$.

Ascending order: $2<4<7<8$

Descending order: $8>7>4>2$

The greatest 4-digits number $=8742$

The smallest 4-digit number $=2478$