Xiaogang bought 2.5 kilograms of sugar, gave the salesperson 20 yuan, got back 1 yuan, how much is the average price per kilogram of sugar.
小刚买了2.5千克糖，给售货员20元钱，找回l元，平均每千克糖多少元．
<gadget id="calculator">20 - 1</gadget>
<output>19</output>

<gadget id="calculator">19 / 2.5</gadget>
<output>7.6</output>

<result>7.6</result>