A construction worker prepares a concrete with 2 parts of cement, 3 parts of sand and 5 parts of stone. There are 200 kilograms more stones than sand in this concrete, how many kilograms of cement are needed?
建筑工人用2份水泥、3份沙子和5份石子配制一种混凝土．这种混凝土中石子比沙子多200千克，需要水泥多少千克？
<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">200 / 2</gadget>
<output>100</output>

<gadget id="calculator">100 * 2</gadget>
<output>200</output>

<result>200</result>