Take 100 fish and mark them and put them in the fish pond. Take out 500 fish for the second time, and 2 of them are marked. How many fish are there in the fish pond?
取100条鱼做上记号放会鱼池，第二次取出500条鱼，有2条有记号，鱼池中大约有多少条鱼．
<gadget id="calculator">100 / 2</gadget>
<output>50</output>

<gadget id="calculator">50 * 500</gadget>
<output>25_000</output>

<result>25_000</result>