Xiao Gang and Xiao Qiang start from the same place on a 400-meter circular runway at the same time. They meet after 50 seconds. It is known that Xiao Gang runs 3.5 meters per second. How many meters does Xiao Qiang run per second?
小刚与小强在400米的环形跑道上，从同一地点相背而行同时出发，50秒之后相遇，已知小刚每秒跑3.5米，求小强每秒跑多少米？
<gadget id="calculator">400 / 50</gadget>
<output>8</output>

<gadget id="calculator">8 - 3.5</gadget>
<output>4.5</output>

<result>4.5</result>