By looking up information, we know that in order to maintain life, each person needs about 2.5 liters of water per day, and how many liters of water are needed by 5 million people per day.
通过查找资料知道为了维持生命，每人每天需要约2.5升水，500万人每天大约需要多少升水．
<gadget id="calculator">500 * 10_000</gadget>
<output>5_000_000</output>

<gadget id="calculator">5_000_000 * 2.5</gadget>
<output>12_500_000</output>

<result>12_500_000</result>