Dad bought 4.5 kilograms of bananas, paid the salesperson 30 yuan, and the salesperson gave him 7.5 yuan. How much is a kilogram of bananas?
爸爸买了4.5千克香蕉，付给售货员30元，售货员找给他7.5元．每千克香蕉多少元？
<gadget id="calculator">30 - 7.5</gadget>
<output>22.5</output>

<gadget id="calculator">22.5 / 4.5</gadget>
<output>5</output>

<result>5</result>