The price of a commodity is reduced seasonally, and the current retail price is 78 yuan, which is 19.5 yuan lower than the original price. How much is the discount?
某商品季节性降价，现零售价是78元，比原价降低了19.5元．打了几折？
<gadget id="calculator">78 + 19.5</gadget>
<output>97.5</output>

<gadget id="calculator">78 / 97.5</gadget>
<output>0.8</output>

<result>0.8</result>