A commodity with a purchase price of $250 and a selling price of $300. How much profit can be obtained after the sale of this commodity accounts for the cost.
一种商品，进货价是250元，售价是300元．这种商品卖出后所能获得的利润占成本的多少．
<gadget id="calculator">300 - 250</gadget>
<output>50</output>

<gadget id="calculator">50 / 250</gadget>
<output>1/5 = around 0.2</output>

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