A disinfectant packaging paper stated: When cleaning the bathtub, the disinfectant and water should be prepared at a ratio of 1:400. Teacher Chen poured out 10 grams of this disinfectant to clean the bathtub. How many kilograms of water are needed to prepare it?
一种消毒液包装纸上写明：清洗浴缸时需要将消毒液和清水按1﹕400配制．陈老师倒出这种消毒液10克清洗浴缸，需要多少千克清水配制？
<gadget id="calculator">1 / 400</gadget>
<output>1/400 = around 0.0025</output>

<gadget id="calculator">10 / (1/400) / 1_000</gadget>
<output>4</output>

<result>4</result>