kind of concrete, in which cement, sand, and stones are prepared according to the ratio of 3:4:5, to prepare 3000 tons of this concrete, how many tons of stones should be prepared?
一种混凝土，其中水泥、沙子、石子按3：4：5配制而成，要配制这种混凝土3000吨，应准备石子多少吨？
<gadget id="calculator">3 + 4 + 5</gadget>
<output>12</output>

<gadget id="calculator">5 / 12</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">300 * (5/12)</gadget>
<output>125</output>

<result>125</result>