A bucket is filled with half a bucket of salt water. The weight ratio of salt to water in the salt water is (1/20). If 200 grams of salt are added to the bucket, the concentration of the salt water should not change. How many more kilograms of water should be added to the bucket?
水桶里装有半桶盐水，盐水中盐和水的重量比是(1/20)，如果向桶中加入200克盐，要使这种盐水的浓度不变．还应向桶中加入水多少千克？
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">200 / (1/20) / 1_000</gadget>
<output>4</output>

<result>4</result>