Mom bought 12.5 kilograms of apples, paid the cashier 50 yuan, and the cashier got back 18.75 yuan. How much is an apple per kilogram?
妈妈买了12.5千克的苹果，付给收银员50元，收银员找回18.75元．每千克苹果多少元？
<gadget id="calculator">50 - 18.75</gadget>
<output>31.25</output>

<gadget id="calculator">31.25 / 12.5</gadget>
<output>2.5</output>

<result>2.5</result>