The current price of a mobile phone is 1,600 yuan, which is 400 yuan cheaper than the original price. How much is it cheaper?
一部手机现价1600元，比原价便宜了400元，便宜了百分之几？
<gadget id="calculator">1_600 + 400</gadget>
<output>2_000</output>

<gadget id="calculator">400 / 2_000</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>