There are 25 people, 6 of them can sing, 10 can dance, and 9 can play the piano. There are three different ways to select three people to perform singing, dancing and playing the piano.
有25人，其中6人会唱歌，10人会跳舞，9人会弹琴，要选拔3个人分别表演唱歌、跳舞、弹琴三种节目，共有多少种不同的选法．
<gadget id="calculator">6 * 10 * 9</gadget>
<output>540</output>

<result>540</result>