Use a cup to pour water into an empty bottle. If 3 cups of water are poured into it, the weight of the whole bottle is 450 grams; if 7 cups of water are poured into it, the weight of the whole bottle is 630 grams. How many grams does each glass of water weigh?
用一个杯子向一个空瓶里倒水，如果倒进3杯水，则连瓶重450克；如果倒进7杯水，则连瓶重630克．每杯水重多少克．
<gadget id="calculator">630 - 450</gadget>
<output>180</output>

<gadget id="calculator">7 - 3</gadget>
<output>4</output>

<gadget id="calculator">180 / 4</gadget>
<output>45</output>

<result>45</result>