The original price of a kind of clothes is 50 yuan per piece, but now it is 45 yuan per piece. Do you know how much discount the mall is offering? State the quantitative relationship.
一种衣服原价每件50元，现在每件45元，你知道商场正在打几折吗？说出数量关系式．
<gadget id="calculator">45 / 50</gadget>
<output>9/10 = around 0.9</output>

<result>9/10 = around 0.9</result>