(2/5) of a number is 4, what is 25% of this number.
一个数的(2/5)是4，这个数的25%是多少．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">4 / (2/5)</gadget>
<output>10</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">10 * (1/4)</gadget>
<output>5/2 = around 2.5</output>

<result>5/2 = around 2.5</result>