A 12-year-old child needs 50 mg of vitamin C per person. It is known that a certain fruit juice contains about 25 mg of vitamin C per 30 grams. How many grams of this fruit juice does a 12-year-old child need to drink to meet the vitamin C needed for a day.
一个12岁儿童每人需要50毫克的维生素C．已知某种果汁每30克含维尘素C约25毫克，一个12岁的儿童需要喝这种果汁多少克才能满足一天所需要的维生素C．
<gadget id="calculator">50 / 25</gadget>
<output>2</output>

<gadget id="calculator">2 * 30</gadget>
<output>60</output>

<result>60</result>