On a winter morning, Xiao Ming and his father ran in the same direction from the same starting point on a snowy circular track. Dad steps 50 centimeters per step, and Xiao Ming steps 30 centimeters per step. The footprints on the snow overlap from time to time, leaving exactly 1680 footprints after running around. How long is this circular runway?
冬天的早晨，小明和爸爸一前一后在一个有雪的环形跑道上从同一起点朝同一方向跑步锻炼．爸爸每步50厘米，小明每步30厘米，雪地上脚印时有重合，跑完一圈正好留下1680个脚印．这个环形跑道长多少米？
<gadget id="calculator">150 / 5 / 10</gadget>
<output>3</output>

<gadget id="calculator">150 / 3 / 10</gadget>
<output>5</output>

<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">1_680 / 7</gadget>
<output>240</output>

<gadget id="calculator">150 / 100</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">240 * (3/2)</gadget>
<output>360</output>

<result>360</result>