The theme of World Environment Day in 2013 is "Think before eating, practice saving after eating". The experimental primary school launched a food saving activity. This month, the canteen used 340 kilograms of rice, which was 15% less than last month. Last month, the canteen How many kilograms of rice did you use?
2013年世界环境日的主题是"思前、食后、厉行节约"，实验小学开展了节约粮食活动，本月食堂用的大米是340千克，比上个月节约了15%，上个月食堂用了大米多少千克？
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">1 - (3/20)</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">340 / (17/20)</gadget>
<output>400</output>

<result>400</result>