Xiao Ming swims 5 back and forth each time in a 50-meter swimming pool, how many meters does he swim each time?
小明在50米的游泳池里，每次游5个来回，他每次游多少米．
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">50 * 10</gadget>
<output>500</output>

<result>500</result>