The original price of a reading pen is 500 yuan, but now it has dropped to 420 yuan. How much is the reduction?
一款点读笔原价500元，现在降到420元，降低了百分之几？
<gadget id="calculator">500 - 420</gadget>
<output>80</output>

<gadget id="calculator">80 / 500</gadget>
<output>4/25 = around 0.16</output>

<result>4/25 = around 0.16</result>