There are number cards 3, 5, 6, and 0 each, how many different three-digit numbers can be formed.
有数字卡片3、5、6、0各一张，可以组成多少个不同的三位数．
<gadget id="calculator">3 * 3 * 2</gadget>
<output>18</output>

<result>18</result>