The medal weight of the 2012 London Olympic Games is 400 grams. The gold medal is made of gold and silver mixed (gold is plated on the surface), and gold accounts for the total weight (3/40). Please calculate according to the meaning of the score: a gold medal How many grams of gold are there?
2012年伦敦奥运会的奖牌重量为400克，其中金牌是金、银混合制作(金镀在表面)，金占总重量的(3/40)，请根据分数的意义算一算：一枚金牌中有多少克金？
<gadget id="calculator">3 / 40</gadget>
<output>3/40 = around 0.075</output>

<gadget id="calculator">400 * (3/40)</gadget>
<output>30</output>

<result>30</result>