The circumference of the earth's equator is about 40,000 kilometers, which is 20,000 kilometers less than (1/5) the distance traveled by light per second. How many kilometers does light travel per second?
地球赤道的周长大约是4万千米，比光每秒传播距离的(1/5)少2万千米．光每秒传播多少万千米？
<gadget id="calculator">4 + 2</gadget>
<output>6</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">6 / (1/5)</gadget>
<output>30</output>

<result>30</result>