Use the three numbers 1, 2, and 9 to form a three-digit number divisible by 3. How many ways are there in total?
用1、2、9这三个数字排成能被3整除的三位数，共有多少种排法．
<gadget id="calculator">3 * 2 * 1</gadget>
<output>6</output>

<result>6</result>