Xiao Ming walks 42 meters per minute, and Xiao Gang walks 36 meters per minute. At this speed, the two walk along the runway at the same time. After 5 minutes, how many meters will Xiao Gang be behind Xiao Ming?
小明每分钟步行42米，小刚每分钟步行36米，照这速度，两人同时沿跑道走，5分钟后，小刚落后小明多少米？
<gadget id="calculator">42 * 5</gadget>
<output>210</output>

<gadget id="calculator">36 * 5</gadget>
<output>180</output>

<gadget id="calculator">210 - 180</gadget>
<output>30</output>

<result>30</result>