The canteen shipped a total of 1800 kg of rice and flour. The rice was flour (1/5). Later, another batch of rice was shipped. At this time, the mass ratio of rice and flour was 1:3. How many kilograms of rice did you ship?
食堂运来大米和面粉共1800千克，大米是面粉的(1/5)，后来又运来一批大米，这时大米和面粉的质量比是1：3．又运来大米多少千克？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">1_800 / (6/5)</gadget>
<output>1_500</output>

<gadget id="calculator">1 + 3</gadget>
<output>4</output>

<gadget id="calculator">1_500 * 4</gadget>
<output>6_000</output>

<gadget id="calculator">6_000 - 1_800</gadget>
<output>4_200</output>

<result>4_200</result>