Use a cup to pour water into an empty jug. If 3 cups of water are poured into it, the weight of the jug is 740 grams; if 5 cups of water are poured into it, the weight of the jug is 980 grams. How many grams does each cup of water weigh?
用一个杯子向一个空水壶里倒水，如果倒进3杯水，连壶重740克；如果倒进5杯水，连壶重980克．每杯水重多少克？
<gadget id="calculator">980 - 740</gadget>
<output>240</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">240 / 2</gadget>
<output>120</output>

<result>120</result>