Uncle Wang took a box of chickens to the market to sell. The box and the chickens weighed 8 kilograms. After selling half of it, there were 4,500 grams left in the box. How much does the empty box weigh?
汪叔叔把一箱小鸡拿到市场去卖，连箱带小鸡共重8千克，卖了一半后，连箱还剩4500克，空箱有多重？
<gadget id="calculator">8 * 1_000</gadget>
<output>8_000</output>

<gadget id="calculator">8_000 - 4_500</gadget>
<output>3_500</output>

<gadget id="calculator">2 / 1_000</gadget>
<output>1/500 = around 0.002</output>

<gadget id="calculator">3_500 * (1/500)</gadget>
<output>7</output>

<gadget id="calculator">8 - 7</gadget>
<output>1</output>

<result>1</result>