Grandma Zhang bought 6.5 kilograms of beans at the vegetable market, paid 20 yuan, and got back 1.8 yuan. How much is it per kilogram of beans?
张奶奶在菜场买了6.5千克豆角，付出20元，找回1.8元，每千克豆角多少元？
<gadget id="calculator">20 - 1.8</gadget>
<output>18.2</output>

<gadget id="calculator">18.2 / 6.5</gadget>
<output>2.8</output>

<result>2.8</result>