45 minutes of exercise on an electric treadmill can produce 900 grams of carbon dioxide. In order to live a low-carbon life, Mr. Li reduces the exercise time on the electric treadmill for 30 minutes every day. How many grams of carbon dioxide emissions can be reduced?
电动跑步机上45分钟的锻炼能产生900克二氧化碳．为了低碳生活，李老师每天减少电动跑步机上30分钟运动时间，可以减少多少克二氧化碳排放？
<gadget id="calculator">900 / 45</gadget>
<output>20</output>

<gadget id="calculator">20 * 30</gadget>
<output>600</output>

<result>600</result>