To prepare a kind of salt water, 5 grams of salt needs to be added with 200 grams of water, the existing water is 800 grams, how many grams of salt is needed?
配置一种盐水，用5克盐需加水200克，现有水800克，需盐多少克．
<gadget id="calculator">5 / 200</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">(1/40) * 800</gadget>
<output>20</output>

<result>20</result>