Xiaolan first filled a glass with half a glass of water and weighed 180 grams; then filled the glass with water and weighed 260 grams. How many grams does a glass of water weigh?
小兰先用一个玻璃杯装了半杯水，称得重180克；又把这个玻璃杯装满水，称得重260克．一杯水净重多少克？
<gadget id="calculator">260 - 180</gadget>
<output>80</output>

<gadget id="calculator">80 * 2</gadget>
<output>160</output>

<result>160</result>