How many ways are there to send 2 of 5 people to water the flowers?
从5人中任意派2人去浇花，有多少种派法．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<result>10</result>