A kind of salt water, the ratio of salt to water is 1:4, to prepare 150 grams of such salt water, how many grams of salt are needed.
一种盐水，盐和水的比是1﹕4，要配制150克这样的盐水，需要盐多少克．
<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">150 * (1/5)</gadget>
<output>30</output>

<result>30</result>