There is a bunch of oranges, take out its (1/21) for the first time, take out the rest (1/20) for the second time, take out the rest (1/19) for the third time, ..., take out the 18th time for the 18th time 17 times the rest (1/4), then how many times the original orange is the last remaining orange.
有一堆桔子，第一次取出它的(1/21)，第二次取出余下的(1/20)，第三次取出第二次余下的(1/19)，…，第18次取出第17次余下的(1/4)，则原来的桔子是最后余下的桔子的多少倍．
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

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

<result>7</result>