Xiaohong bought 2 kilograms of oranges and 5 kilograms of watermelon, a total of 10 yuan. Knowing that watermelon costs 1 yuan per kilogram, ask: how much is orange per kilogram?
小红买了2千克橘子和5千克西瓜，共10元．已知每千克西瓜1元，问：每千克橘子多少元？
<gadget id="calculator">5 * 1</gadget>
<output>5</output>

<gadget id="calculator">10 - 5</gadget>
<output>5</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<result>5/2 = around 2.5</result>