Xiao Ming ran 4 back and forth on a runway, and ran a total of 672 meters. How long is this runway in meters?
小明在一条跑道上跑了4个来回，一共跑了672米，这条跑道长多少米？
<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<gadget id="calculator">672 / 8</gadget>
<output>84</output>

<result>84</result>