To prepare a salt water, the weight ratio of salt to water is 1:20, and the salt is the weight of the salt water.
配制一种盐水，盐和水的重量比是1：20，盐是盐水重量的多少．
<gadget id="calculator">20 / 1</gadget>
<output>20</output>

<gadget id="calculator">1 + 20</gadget>
<output>21</output>

<gadget id="calculator">1 / 21</gadget>
<output>1/21 = around 0.047619</output>

<result>1/21 = around 0.047619</result>