8 students are dancing, each in a group of two, how many ways can there be?
8个同学在跳舞，每两人一组，可以有多少种分法．
<gadget id="calculator">7 / 2</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">8 * (7/2)</gadget>
<output>28</output>

<result>28</result>