Li Hong's home is 685 meters away from the school, and he goes back and forth twice a day. How many meters do he have to walk in total?
李红家离学校685米，每天往返两次，一共要走多少米？
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">685 * 4</gadget>
<output>2_740</output>

<result>2_740</result>