If a batch of goods is shipped in 4 days (4/7), how many days can this batch of goods be shipped.
运一批货物，如果4天运走(4/7)，多少天可以运完这批货物．
<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">(4/7) / 4</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 / (1/7)</gadget>
<output>7</output>

<result>7</result>