During the winter camp, the school has hired 3 vehicles, each of which can accommodate 42 students. After arriving at the destination, every 6 students are divided into an activity group. How many activity groups are there in total?
冬令营活动中学校包了3辆车，每辆车乘坐42名学生，到达目的地后每6名学生分成一个活动小组，问，一共有多少个活动小组？
<gadget id="calculator">3 / 6</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">42 * (1/2)</gadget>
<output>21</output>

<result>21</result>