The original price of a set of books is 500 yuan, and the price is reduced (1/5) on Children's Day. How much is the current price?
一套书原价500元，六一儿童节降价(1/5)销售，现在售价多少元．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">500 - 100</gadget>
<output>400</output>

<result>400</result>