For a distance of 100 meters, Xiao Ming has to walk 160 steps on average. According to this calculation, he needs to walk 640 steps to complete the school's circular playground. What is the approximate circumference of the circular playground in meters?
100米的距离，小明平均要走160步，照这样计算，他走完学校环形操场要走640步，环形操场的周长大约是多少米．
<gadget id="calculator">100 / 160</gadget>
<output>5/8 = around 0.625</output>

<gadget id="calculator">(5/8) * 640</gadget>
<output>400</output>

<result>400</result>