The price of an electric kettle in a supermarket is 400 yuan, which is 100 yuan cheaper than the original price. By how much is the price of this electric kettle reduced?
超市里一种电水壶的售价是400元，比原价便宜100元，这种电水壶的价格降低了百分之几？
<gadget id="calculator">400 + 100</gadget>
<output>500</output>

<gadget id="calculator">100 / 500</gadget>
<output>1/5 = around 0.2</output>

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