20% of a number is exactly 2/5 of 40. What is this number?
一个数的20%正好是40的(2/5)，这个数是多少．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(2/5) / (1/5)</gadget>
<output>2</output>

<gadget id="calculator">40 * 2</gadget>
<output>80</output>

<result>80</result>