The uncle in the cafeteria bought 4.5 kilograms of cucumbers, handed them to the salesperson for 10 yuan, and got back 1.9 yuan. How much is a kilogram of cucumbers?
食堂的叔叔买了4.5千克的黄瓜，交给售货员10元后，找回1.9元，每千克黄瓜多少元？
<gadget id="calculator">10 - 1.9</gadget>
<output>8.1</output>

<gadget id="calculator">8.1 / 4.5</gadget>
<output>1.8</output>

<result>1.8</result>