The ratio of yellow sand, cement, and water in concrete is 3:2:10, how many tons of yellow sand are needed in 40 tons of concrete.
混凝土中黄沙、水泥、水的比例是3：2：10，40吨混凝土中需要黄沙多少吨．
<gadget id="calculator">3 + 2 + 10</gadget>
<output>15</output>

<gadget id="calculator">3 / 15</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">40 * (1/5)</gadget>
<output>8</output>

<result>8</result>