Grandma Wang bought 2.5 kilograms of bananas, handed them to the salesperson for 10 yuan, and got back 0.5 yuan. How much is a kilogram of bananas?
王奶奶买了2.5千克香蕉，交给售货员10元后，找回0.5元，每千克香蕉多少钱？
<gadget id="calculator">10 - 0.5</gadget>
<output>9.5</output>

<gadget id="calculator">9.5 / 2.5</gadget>
<output>3.8</output>

<result>3.8</result>