Put some water in a glass bottle. If the water is doubled to its original volume, then the water and the bottle weigh 500 grams in total. If the water is added to the original 4 times, then the total weight of the water and the bottle is 900 grams. How many grams does this glass bottle weigh?
一个玻璃瓶里放了一些水．如果把水加到原来的2倍，那么水和瓶共重500克．如果把水加到原来的4倍，那么水和瓶共重900克．这个玻璃瓶重多少克？
<gadget id="calculator">900 - 500</gadget>
<output>400</output>

<gadget id="calculator">500 - 400</gadget>
<output>100</output>

<result>100</result>