To prepare 200 grams of salt water, the ratio of salt to water is 1:4, how many grams of salt should be added.
要配制盐水200克，已知盐与水的比是1：4，需加盐多少克．
<gadget id="calculator">1 + 4</gadget>
<output>5</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">200 * (1/5)</gadget>
<output>40</output>

<result>40</result>