20% of a number is 100, what is the number?
一个数的20%是100，这个数的是多少．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">100 / (1/5)</gadget>
<output>500</output>

<result>500</result>