A swimming pool is 20 meters long. Xiao Ming has already swam one back and forth in the swimming pool. How many meters has he swum in total?
一个游泳池长20米，小明在游泳池中已经游了1个来回，他共游了多少米．
<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<result>40</result>