Question

重新排列 $2004$ 中的四个数字，可以组成多少个不同的四位数？

How many different four-digit numbers can be formed by rearranging the four digits in $2004$ ?

$4$

$6$

$16$

$24$

$81$

有 $2$ 个非零数字可以作为千位数字。

选定后，需要安排另外 $3$ 个数字。另一个非零数字有 $3$ 个位置可放。

因此共有 $2 \cdot 3 = 6$ 个可能的数。

所以正确答案是 B。

Note that there are $2$ non-zero digits that could be the thousands digit.

After choosing that, we need to arrange the other $3$ digits. There are $3$ spots for the other non-zero digit.

This gives us $2 \cdot 3 = 6$ possible numbers.

Thus, B is the correct answer.