Aunt Wang went to the supermarket to buy fruit. She bought 4.8 kilograms of apples, paid 50 yuan, and got back 28.4 yuan. How much is an apple per kilogram?
王阿姨去超市买水果．她买了4.8千克苹果，付出50元，找回28.4元．每千克苹果多少元？
<gadget id="calculator">50 - 28.4</gadget>
<output>21.6</output>

<gadget id="calculator">21.6 / 4.8</gadget>
<output>4.5</output>

<result>4.5</result>