How many different plans are there for choosing 2 of 4 students to play chess?
从4个同学中选2人参加下象棋，有多少种不同的方案．
<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">4 * (3/2)</gadget>
<output>6</output>

<result>6</result>