Aunt Zhao bought 4.25 kilograms of "Xu Fuji" biscuits in the supermarket. She paid 40 yuan and got back 9.4 yuan. How much is a kilogram of biscuits?
赵阿姨在超市买了4.25千克的"徐福记"饼干，付出40元，找回9.4元，每千克饼干多少钱？
<gadget id="calculator">40 - 9.4</gadget>
<output>30.6</output>

<gadget id="calculator">30.6 / 4.25</gadget>
<output>7.2</output>

<result>7.2</result>