There are 300 grams of salt water with a salt content of (1/10), how many grams of salt should be added to turn it into a salt water with a salt content of (1/4)?
现有含盐量为(1/10)的盐水300克，要把它变成含盐量为(1/4)的盐水，需要加盐多少克？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">300 * (9/10)</gadget>
<output>270</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">270 / (3/4)</gadget>
<output>360</output>

<gadget id="calculator">360 - 270</gadget>
<output>90</output>

<result>90</result>