The swimming pool is 50 meters long. Xiao Min swam 4 back and forth, how many meters did one swim.
游泳池长50米，小敏游了4个来回，一个游了多少米．
<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<gadget id="calculator">50 * 8</gadget>
<output>400</output>

<result>400</result>