Xiaoqiang's home is 3 kilometers away from the school. Xiaoqiang goes to school twice a day, how many kilometers does he have to walk back and forth?
小强家离学校3千米，小强每天上两次学，来回要走多少千米．
<gadget id="calculator">3 * 2 * 2</gadget>
<output>12</output>

<result>12</result>