It takes 7 days to build a 6-kilometer road. How much can be repaired in 4 days
修一段6千米的路，7天可以修完．4天可以修多少
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(1/7) * 4</gadget>
<output>4/7 = around 0.571429</output>

<result>4/7 = around 0.571429</result>