How many kilograms of cement is needed to make 1000 kg of concrete by mixing cement and sand in a ratio of 1:3?
把水泥和沙子按1：3混合制成混凝土1000千克，需要水泥多少千克．
<gadget id="calculator">1 + 3</gadget>
<output>4</output>

<gadget id="calculator">1_000 / 4</gadget>
<output>250</output>

<gadget id="calculator">250 * 1</gadget>
<output>250</output>

<result>250</result>