A cup (1/4) L of fresh milk contains about (3/10) g of calcium, which accounts for (3/8) of an adult's daily calcium needs. How much calcium does an adult need per day? (First write out the quantitative relationship to solve the problem, and then answer)
一杯(1/4)L的鲜牛奶大约含有(3/10)g的钙质，占一个成年人一天所需钙质的(3/8)．一个成年人一天需要多少钙质？(先写出解决问题的数量关系，再解答)
<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">(3/10) / (3/8)</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>