Aunt Zhang went to the market and bought 6 kilograms of beans, paid 15 yuan, and got back 1.8 yuan. How much is it per kilogram of beans?
张阿姨到市场买了6千克豆角，付出15元，找回1.8元．每千克豆角多少元？
<gadget id="calculator">15 - 1.8</gadget>
<output>13.2</output>

<gadget id="calculator">13.2 / 6</gadget>
<output>2.2</output>

<result>2.2</result>