Mom brought 50 yuan to buy apples. She bought 5 kilograms of apples and got back 9.2 yuan. How much is the apple bought by mother per kilogram?
妈妈带了50元钱去买苹果，她买了5千克苹果，找回了9.2元钱．妈妈买的苹果每千克多少元？
<gadget id="calculator">50 - 9.2</gadget>
<output>40.8</output>

<gadget id="calculator">40.8 / 5</gadget>
<output>8.16</output>

<result>8.16</result>